Nonaqueous secondary battery having multiple-layered negative electrode

ABSTRACT

This invention provides a cylinder type nonaqueous secondary battery which comprises a positive electrode active material comprising a lithium-containing transition metal oxide, a composite oxide or composite chalcogen negative electrode material capable of intercalating and deintercalating lithium and a nonaqueous electrolyte containing a lithium metal salt, wherein high discharging capacity and excellent charge and discharge cycle characteristics are obtained by mounting a metal foil mainly comprising lithium in advance in a coiled group in which a current collector sheet coated with the positive electrode active material (positive electrode sheet), another current collector sheet coated with the negative electrode material (negative electrode sheet) and a separator are coiled in a spiral form.

TECHNICAL FIELD

This invention relates to a nonaqueous secondary battery in which chargeand discharge capacities and cycle characteristics are improved.

BACKGROUND ART

Lithium metals and lithium alloys are used as typical negative electrodematerials in nonaqueous secondary batteries, but, when they are used,the lithium metal grows into a dendritic form during charging anddischarging to generate a so-called dendrite which becomes a cause ofinternal short, or the high activity of the dendrite itself poses apossible danger of causing firing and the like.

On the other hand, calcined carbonaceous materials capable of reverselyintercalating and deintercalating lithium have been put into practicaluse. Such carbonaceous material has a relatively small density whichposes a disadvantage of having low capacity per volume. Because of this,use of the carbon material by pressing or laminating lithium foilthereto is described in JP-A-5-151995 (the term "JP-A" as used hereinmeans an "unexamined published Japanese patent application"), but itcannot resolve the aforementioned problems.

Also, methods in which oxides of Sn, V, Si, B, Zr and the like orcomposite oxides thereof are used in negative electrode materials havebeen proposed (JP-A-5-174818, JP-A-6-60867, JP-A-6-275267,JP-A-6-325765, JP-A-6-338324, EP-615296). It is said that negativeelectrodes of these oxides or composite oxides provide nonaqueoussecondary batteries having a large charging capacity of 3 to 3.6 V classwhen combined with a positive electrode of a certain type oflithium-containing transition metal compound and have markedly highsafety, because they hardly generate dendrite within the practicalrange. However, batteries in which these materials are used have aserious problem in that their charge and discharge characteristics arenot sufficient, and their charge and discharge efficiency in initialcycles is particularly low. That is, it is assumed that a portion oflithium molecules intercalated in the negative electrode during thecharging step cause a plurality of irreversible side reactions duringseveral initial stage cycles, so that lithium does not move into thepositive electrode side during the discharging step, thereby causingcapacity loss due to unnecessarily consumed lithium in the positiveelectrode. In order to compensate for such a capacity loss, it may bepossible to intercalate lithium into the negative electrode material inadvance in an amount corresponding to the capacity loss, but sufficienteffect has not been obtained yet by such means.

The object of the present invention is to obtain a nonaqueous secondarybattery which has 1) high charge and discharge capacities and excellentcharge and discharge cycle characteristics and 2) a high energy density.

DISCLOSURE OF THE INVENTION

The present invention has been achieved by a cylinder type nonaqueoussecondary battery which comprises a positive electrode active materialcomprising a lithium-containing transition metal oxide, a compositeoxide or composite chalcogen negative electrode material capable ofintercalating and deintercalating lithium and a nonaqueous electrolytecontaining a lithium metal salt, wherein a metal foil mainly comprisinglithium is mounted in advance on a coiled group in which a currentcollector sheet coated with said positive electrode active material(positive electrode sheet), another current collector sheet coated withsaid negative electrode material (negative electrode sheet) and aseparator are coiled in a spiral form.

A nonaqueous secondary battery having a high energy density as an objectof the present invention is substantially achieved when a part of orentire portion of the metal foil mainly comprising lithium introducedinto the coiled group is finally incorporated into the negativeelectrode material. As a means for intercalating lithium in the negativeelectrode material, a method is possible in which lithium is introducedinto the negative electrode material by forming a local electrochemicaljunction in a state that the negative electrode sheet and the metal foilmainly comprising lithium are electrically conducted. In this method,lithium is supplied into the negative electrode material through theformation of a local electrochemical junction comprising the metal foilmainly comprising lithium, which is the most efficient lithium supplysource per unit volume, and the negative electrode material, so that itis possible to supply lithium in a corresponding amount to the sidereactions without using the positive electrode active material.

The part on which the metal mainly comprising lithium is pressed is anyoptional area on the negative electrode sheet but preferably on thenegative electrode material mixture layer coated with the negativeelectrode material or on the current collector metal on which thenegative electrode material is not coated. Most preferably, it is on thenegative electrode material mixture layer.

Preliminary intercalation of lithium into the negative electrodematerial may be effected by a method in which the metal foil mainlycomprising lithium is laminated on the negative electrode sheet toassemble a nonaqueous secondary battery together with a separator andthe positive electrode sheet and then an electrolytic solution isinjected therein and subjected to aging for a predetermined period oftime.

The metal foil mainly comprising lithium to be used in the preliminaryintercalation may have a lithium content of preferably 90% or more, morepreferably 98% or more.

Aluminum is desirable as a metal other than lithium.

It is possible to optionally control the intercalating amount of lithiumby the laminating amount of lithium. The amount of lithium forpreliminary intercalation is preferably from 0.5 to 4.0 equivalents,more preferably from 1 to 3.5 equivalents, most preferably from 1.2 to3.2 equivalents, based on the negative electrode material.

Preliminary intercalation of lithium into the negative electrodematerial in an amount of more than 4.0 equivalents is not desirablebecause of the extreme deterioration of cycle characteristics. It ispossible that local overcharge of the negative electrode active materialis a cause of the deterioration of cycle characteristics, though it isnot strictly clear.

In other words, the amount of lithium for preliminary intercalation ispreferably from 0.005 to 0.2 g, more preferably from 0.04 to 0.15 g,based on the unit weight of the negative electrode material. Whenconverted to the unit volume of the negative electrode sheet, it may bepreferably from 1 to 30 g/m², more preferably from 4 to 16 g/m².

Pressing of the metal foil mainly comprising lithium on the negativeelectrode sheet can be made easily by press roller and the like. Whenthe metal foil mainly comprising lithium is pressed on the negativeelectrode collector metal, the foil may have a thickness of preferablyfrom 50 μm to 500 μm, more preferably from 50 to 250 μm. When the metalfoil mainly comprising lithium is pressed on the negative electrodematerial mixture layer, the foil may have a thickness of preferably from5 to 150 μm, more preferably from 5 to 100 μm, most preferably from 10to 75 μm.

The battery of the present invention may be subjected to the maincharging immediately after assembling, but it is desirable to carry outaging before the main charging, in order to effect uniform diffusion oflithium in the negative electrode material. The term "main charging" asused herein means a charging carried out by setting the final voltage tothe desirable voltage range of the battery of the present invention, andthe desirable voltage range is 3.8 to 4.3 V as the final chargingvoltage. The aging may be carried out preferably at a temperature offrom 0 to 80° C. for a period of from 1 hour to 60 days, more preferablyat 20 to 70° C. for 10 hours to 30 days.

It is further desirable to set the open circuit voltage of the batteryto a preferable range during the aging, in order to effect uniformintercalation of lithium in the negative electrode material.

The open circuit voltage of this case is preferably 1.5 to 3.8 V, morepreferably 1.5 to 3.5 V. Setting of the battery open circuit voltage tothe preferred range may be effected by charging or charging anddischarging the battery after injection of electrolytic solution andcrimping. Timing of the charging or charging and discharging ispreferably between immediately after the commencement of aging, namelyfrom immediately after cramping to 60 days after the commencement ofaging. More preferably, it may be between 1 hour and 30 days after thecommencement of aging, most preferably between 3 hours and 10 days afterthe commencement of aging. The aging temperature of this case is withinthe range of preferably from 0 to 80° C., more preferably from 10 to 70°C., most preferably from 20 to 60° C. During the aging, the battery maybe placed vertically or horizontally or continuously rolled.

When the open circuit voltage is set by charging, it is desirable toeffect the charging by constant voltage charging under a currentcondition of from 0.05 to 4.1 mA per 1 cm² of the surface of thenegative electrode sheet. The current value is more preferably from 0.1to 3.0 mA, most preferably from 0.15 to 2.4 mA. The charging period ispreferably from 0.2 to 20 hours, more preferably from 0.5 to 10 hours,most preferably from 0.5 to 5 hours.

When the open circuit voltage is set by charging and discharging, acombination of constant voltage charging and constant currentdischarging is desirable. Final charging voltage of the constant voltagecharging is within the range of preferably from 2.0 to 3.8 V, morepreferably from 2.5 to 3.5 V, most preferably from 2.7 to 3.5 V. Finaldischarging voltage of the constant current discharging is within therange of preferably from 1.0 to 3.5 V, more preferably from 1.5 to 3.3V, most preferably from 2.5 to 3.1 V. The current condition in this caseis within the range of preferably from 0.05 to 4.5 mA, more preferablyfrom 0.1 to 3.0 mA, most preferably from 0.15 to 2.4 mA, per 1 cm² ofthe surface of the negative electrode sheet, in both cases of chargingand discharging. The charging period is preferably from 0.2 to 20 hours,more preferably from 0.5 to 10 hours, most preferably from 0.5 to 5hours. The number of charging and discharging cycles is preferably from1 to 500 cycles, more preferably from 5 to 200 cycles, most preferablyfrom 10 to 150 cycles. When the open circuit voltage is adjusted bycharging and discharging, the adjustment may be completed either bycharging or discharging.

The aforementioned charging or charging and discharging may be carriedout at a temperature of preferably from 0 to 60° C., more preferablyfrom 10 to 50° C., most preferably from 20 to 40° C. The charging orcharging and discharging procedure may be carried out optional timesduring the aging, but preferably 1 to 3 times, more preferably onlyonce.

The metal foil mainly comprising lithium may be pressed directly on thenegative electrode material-containing negative electrode materialmixture layer, but it is more desirable to arrange at least one layer ofan auxiliary layer containing water insoluble particles on the mixturelayer and press the foil on the auxiliary layer, in view of uniformintercalation of lithium. This auxiliary layer does not contain thenegative electrode material.

Arrangement of a layer which is different from the active material, suchas a protective layer, on the electrode surface has been examined in theprior art, and, in the case of negative electrodes of lithium metals andalloys, arrangement of protective layers comprising carbon materials andmetal powder-containing carbon has been described in JP-A-4-229562, U.S.Pat. No. 5,387,479 and JP-A-3-297072. However, the object of thesepatents is to protect active part on the lithium metal surface, therebypreventing decomposition of the electrolytic solution caused by itscontact with the active part and formation of a passive film from thedecomposed products and the like, so that the construction and object ofthese inventions are different from those of the metal oxide negativeelectrode of the present invention.

JP-A-61-263069 describes that a transition metal oxide is used as thenegative electrode material and its surface is coated with anion-conductive solid electrolyte, and arrangement of the solidelectrolyte film on the transition metal oxide layer by spattering isdescribed in its Examples. Similar to the case of the aforementionedpatents, the object of this patent is to prevent precipitation ofdendritic form-lithium and decomposition of electrolytic solution, whichtherefore is different from the object of the instant invention. Inaddition, the ion-conductive solid electrolyte is not desirable becauseof its solubility in water and hygroscopicity.

Also, JP-A-61-7577 describes about a protective layer comprised of amaterial having both electric conductivity and ionic conductivity,covered on the surface of positive electrode, and describes that oxidesof tungsten, molybdenum and vanadium are desirable as the materialhaving electric-ionic mixture conductivity. However, these oxides arecompounds capable of intercalating and deintercalating lithium, so thatare not desirable in the present invention.

According to the present invention, the auxiliary layer to be arrangedon the negative electrode sheet comprises at least one layer, and may beconstructed by a plurality of the same or different layers. Theseauxiliary layers comprise water insoluble electrically conductiveparticles and a binder. The binder to be used in the formation of anelectrode material mixture, which will be described later, can be usedin this case. The electrically conductive particles to be included inthe auxiliary layer may be used in an amount of preferably 2.5% byweight to 96% by weight, more preferably 5% by weight to 95% by weight,most preferably 10% by weight to 93% by weight.

Examples of the water insoluble electrically conductive particles of thepresent invention include particles of metals, metal oxides, metalfibers, carbon fibers and carbon black, graphite and the like carbonparticles. These particles may have a solubility of 100 ppm or less inwater, but preferably be insoluble in water. Of these water insolubleelectrically conductive particles, those which have low reactivity withalkali metals, particularly with lithium, are desirable, and metalpowders and carbon particles are more desirable. Theparticle-constituting elements may have an electrical resistivity of5×10⁹ Ω·m or less at 20° C.

As the metal powders, those which have low reactivity with lithium,namely metals which hardly form lithium alloys, are preferred, and theirillustrative examples include copper, nickel, iron, chromium,molybdenum, titanium, tungsten and tantalum. These metal powder may havea needle shape, a columnar shape, a plate shape or a mass shape, and amaximum particle size of preferably 0.02 μm to 20 μm, more preferably0.1 μm to 10 μm. It is desirable that the surface of these metal powdersis not oxidized, and if oxidized, it is desirable to treat them withheat in a reduced atmosphere.

As the carbon particles, carbon materials generally known as conductivematerials to be combination-used with non-conductive electrode activematerials can be used. Examples of these materials include thermalblack, furnace black, channel black, lamp black or the like carbonblack, flake graphite, scale graphite, earthy graphite or the likenatural graphite, synthetic graphite, carbon fibers and the like. Inorder to mix and disperse these carbon particles with a binder, it isdesirable to use carbon black and graphite in combination. As the carbonblack, acetylene black and Ketjen black are preferred. The carbonparticles may have a particle size of preferably 0.01 μm to 20 μm, morepreferably 0.02 μm to 10 μm.

The aforementioned auxiliary layer may contain particles having noconductivity, in order to improve strength of the coated layer. Examplesof such the particles include teflon fine powder, SiC, aluminum nitride,alumina, zirconia, magnesia, mullite, forsterite and steatite. It isdesirable to use these particles in an amount of 0.01 time to 10 timesof the conductive particles.

When the negative electrode is formed by coating the material mixture onboth sides of the current collector, these auxiliary layers may becoated on both sides or one side thereof.

Coating method of the auxiliary layer may be effected by a method inwhich a material mixture mainly comprising a metal or metalloid oxide asa material capable of reversely intercalating and deintercalatinglithium is coated on the current collector and then the auxiliary layeris coated by successive coating method or by a simultaneous coatingmethod in which the material mixture layer and the auxiliary layer aresimultaneously coated.

Next, the protective layer to be arranged on the positive electrodesheet is described below. The protective layer comprises at least onelayer and may be constructed by a plurality of the same or differentlayers. These protective layers may be layers having substantially noelectric conductivity, namely insulating layers, or electricallyconductive layers similar to the case of the negative electrode sheet.In addition, the protecting layer may have a shape in which aninsulating layer and an electrically conductive layer are laminated. Theprotective layer may have a thickness of preferably 0.2 μm to 40 μm,more preferably 0.3 μm to 20 μm. Also it is desirable that theseparticle-containing protective layers does not melt at 300° C. or lessor form new films.

When the protective layer comprise water insoluble conductive particlesand a binder, the electrically conductive particles used in theauxiliary layer of negative electrode sheet can be used. Preferred type,size and the like of the electrically conductive particles are the sameas those in the case of the negative electrode sheet.

When the protective layers are insulating type, these layers maypreferably contain organic or inorganic particles. These particles mayhave a particle size of preferably 0.1 μm to 20 μm, more preferably 0.2μm to 15 μm. Preferred organic particles are crosslinked latex orfluorocarbon resin in the form of powder, which do not decompose at 300°C. or lower or form films. More preferred is fine powder of teflon.

Examples of the inorganic particles include carbides, suicides,nitrides, sulfides and oxides of metal and metalloid elements.

Among carbides, suicides and nitrides, SiC, aluminum nitride (AlN), BNand BP are preferred because of their high insulating capacity andchemical stability, and SiC in which BeO, Be or BN is used as asintering aid is particularly preferred.

Among chalcogenides, oxides are preferred, particularly those which arehardly oxidized or reduced are preferred. Examples of such the oxidesinclude Al₂ O₃, As₄ O₆, B₂ O₃, BaO, BeO, CaO, Li₂ O, K₂ O, Na₂ O, In₂O₃, MgO, Sb₂ O₅, SiO₂, SrO and ZrO₄. Of these oxides, Al₂ O₃, BaO, BeO,CaO, K₂ O, Na₂ O, MgO, SiO₂, SrO and ZrO₄ are particularly preferred.These oxides may be used alone or as a composite oxide. Examples ofpreferred compound as the composite oxide include mullite (3Al₂O₃.2SiO₂), steatite (MgO.SiO₂), forsterite (2MgO.SiO₂), cordierite(2MgO.2Al₂ O₃.5SiO₂) and the like.

These insulating inorganic compound particles may be used by adjustingtheir particle size to preferably 0.1 μm to 20 μm, more preferably 0.2μm to 15 μm, by controlling their formation conditions or by a grindingor the like means.

The protective layer is formed using these electrically conductiveparticles and/or particles having substantially no conductivity and abinder. As the binder, a binder to be used in the formation of theelectrode material mixture, which will be described later, can be used.These particles may be used in an amount of preferably 40% by weight to96% by weight, more preferably 50% by weight to 94% by weight, based onthe total weight of the particles and binder.

The other materials for use in the preparation of the nonaqueoussecondary battery of the present invention and production processesthereof are described in detail below.

The positive and negative electrodes to be used in the nonaqueoussecondary battery of the present invention can be prepared by coating apositive electrode material mixture or a negative electrode materialmixture on a current collector. In addition to a positive electrodeactive material or a negative electrode active material, the positive ornegative electrode material mixture may also contain an electricallyconductive agent, a binder, a dispersing agent, a filler, an ionicconductive agent, a pressure reinforcing agent and various additives.

Next, a method for the pressing of a metal foil mainly comprisinglithium on a negative electrode material mixture layer or on anauxiliary layer arranged on the negative electrode material mixturelayer is illustratively described below.

With regard to the laminating pattern, it is desirable to laminate ametal foil having a constant thickness on the entire area of thenegative electrode sheet, but, since lithium preliminary intercalatedinto the negative electrode material diffuses gradually in the negativeelectrode material by aging, the foil may be laminated not on the entiresheet but partially in the shape of a stripe, a frame or a disc. In thecase of such a partial laminating, uniform preliminary intercalation oflithium can be achieved by controlling size of the metal foil. It isdesirable to laminate the stripe in a lengthwise direction or crosswisedirection against the negative electrode sheet, in view of theproduction suitability. Constant laminating distance is desirable, butirregular distance may also be employed. A lattice like pattern preparedby combining lengthwise direction and crosswise direction may also beused, which is particularly desirable for the uniform preliminaryintercalation of lithium. Size of the stripe is optionally selecteddepending on the size of the negative electrode sheet, but the stripemay have a width of preferably from a half the length of the side of thenegative electrode sheet to 0.5 mm. More preferably, it may be from ahalf the length of the side of the negative electrode sheet to 1 mm,more preferably from a half the length of the side of the negativeelectrode sheet to 1.5 mm. The width of stripe of smaller than 0.5 mmwould cause a difficulty in cutting and handling the metal foil. Theterm "width of stripe" as used herein means longitudinal direction ofthe electrode sheet. Also, it is particularly desirable that the lengthof stripe is equal to the width of the electrode.

When the stripe is laminated, patterns on the front and back sides ofthe sheet may be the same or different from each other. It is desirableto apply the metal foil to the back side of the surface where the metalfoil is not applied.

When laminated in a frame shape, the frame may have any of triangular topolygonal shapes, but a quadrangular shape (a rectangle, a square or thelike) is particularly preferred. From the handling point of view, theframe may have a size of preferably 4 mm² or more (2 mm×2 mm in the caseof a square), more preferably 16 mm² or more (4 mm×4 mm in the case of asquare).

Typical examples of the laminating pattern of lithium and negativeelectrode sheet are shown in FIG. 3. FIG. 3(a) is a frame pattern, andFIGS. 3(b) and (c) are stripe patterns.

When laminated in a disc form, the disc may have a completely roundshape, an elliptical shape or any other circular form. From the handlingpoint of view, the disc may have a size of preferably 4 mm² or more,more preferably 16 mm² or more.

In the case of partial laminating, any one of stripe, frame and discpatterns or a combination of two or more of them may be used.

In the negative electrode sheet, coating ratio of the metal foillamination may be preferably 10 to 100%, more preferably 15 to 100%,most preferably 20 to 100%. The ratio of smaller than 10% would causeununiform preliminary intercalation of lithium.

In this method, corresponding amount of lithium consumed by sidereactions is supplied into the negative electrode material not from thepositive electrode active material but from the laminated lithium.

A roll transfer method or a board transfer method is used for laminatingthe metal material mainly comprising lithium on the negative electrodesheet. In the roll transfer method, the metal foil cut to an optionalsize is once adhered to a roller and then continuously adhered to thenegative electrode sheet by calender press. A twin roller system isdesirable in view of the improvement of adhesiveness. Though notparticularly limited, the roller may have a diameter of preferably from0.5 to 100 cm, more preferably 1 to 50 cm. As the roller material, it isdesirable to use a material which hardly reacts with lithium, whichincludes polyolefin (polyethylene, polypropylene or the like), teflon,polyimide, polycarbonate and the like polymers and stainless steel,molybdenum and the like metals. In the board transfer method, the metalfoil cut to an optional size is once adhered on a flat board and thenadhered on the negative electrode sheet by pressing. In this case, theadhesion is not continuous, and one or two or more sheets of the metalfoil may be adhered simultaneously.

As the board material, the same material as described in the rolltransfer method may be used preferably. In both of the roll transfer andboard transfer methods, the laminating pressure may be preferably from0.1 to 150 kg/cm², more preferably from 1 to 100 kg/cm².

Prior to its adhesion to a roller or a board, the metal foil is cut toan optional size, preferably using a cutter, a rolling cutter or acutter for sewing machine. When the cutting is carried out, one or amixture of solvents inert to lithium may be used, which include paraffinoil, carbonates (diethyl carbonate, ethylene carbonate, propylenecarbonate and the like), esters (ethyl acetate, ethyl propionate and thelike), ethers (diisopropyl ether, diethyl ether and the like) andaromatic hydrocarbons (benzene, toluene, xylene and the like).

The surface of the roller or board may be either smooth or non-smooth(such as an embossing-finished surface).

It is desirable to store the metal foil mainly comprising lithium in theair at a dew point of -10 to -80° C. until its contact with theelectrolytic solution or to expose it at least once to a gaseousatmosphere containing 0.1 to 10% of carbon dioxide at a dew point of -10to -80° C.

In the case of the gaseous atmosphere, it means an average value in atreating room or zone and does not mean a local value. That is, when thecarbon dioxide content is described to be 0.1% to 10%, it includes acase of locally exceeding 10%. It is desirable to store the metal mainlycomprising lithium in the aforementioned gaseous atmosphere always untilits contact with the electrolytic solution, and it is desirable to storein the aforementioned gaseous atmosphere at least when the metal mainlycomprising lithium is cut and when the metal mainly comprising lithiumis pressed on the electrode sheet with a pressure. Alternatively, theaforementioned carbonic acid gas may be blown from a nozzle or the likein the midst of the cutting or pressing of the metal mainly comprisinglithium. By the treatment with carbon dioxide under a condition of lowdew point, stable surface-film of lithium carbonate is formed, anddeterioration of lithium by oxygen, nitrogen, water and the like isprevented. In addition, since lithium carbonate is inert to theelectrolytic solution, which will be described later, and has lithiumion-permeability, it protects the surface of the metal mainly comprisinglithium, hardly exerting other actions.

The positive or negative electrode to be used in the present inventionis prepared by coating a material mixture layer containing a positiveelectrode active material or a negative electrode material on a currentcollector. When the positive or negative electrode is in a sheet likeshape, it is desirable to arrange the material mixture layer on bothsides of the current collector, and the material mixture layer on oneside may comprise a plurality of layers. In addition to the positiveelectrode active material or negative electrode material which concernsin the intercalation and deintercalation of light metal ions, thematerial mixture layer also contains a binder, an electricallyconductive material and the like. In addition to the material mixturelayer, the electrode may also have layers which do not contain activematerials, such as a protective layer, an undercoating layer to bearranged on the current collector and an intermediate layer to bearranged between material mixture layers. Preferably, these layershaving no active materials may contain electrically conductiveparticles, insulating particles, binders and the like.

The positive electrode active material to be used in the presentinvention may be a transition metal oxide which can reversely undergointercalation and deintercalation of lithium, and a lithium-containingtransition metal oxide is particularly preferred. Illustrative examplesof these positive electrode active materials are disclosed, for example,in JP-A-61-5262, U.S. Pat. No. 4,302,518, JP-A-63-299056, JP-A-1-294364,JP-B-4-30146 (the term "JP-B" as used herein means an "examined Japanesepatent publication"), U.S. Pat. No. 5,240,794, U.S. Pat. No. 5,153,081,JP-A-4-328,258 and JP-A-5-54,889.

Preferred examples of the lithium-containing transition metal oxidepositive electrode active material to be used in the present inventioninclude oxides of lithium-containing Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Moand W. Also, it may be mixed with other alkali metals than lithium(elements of the groups IA and IIA of the periodic table) and/or Al, Ga,In, Ge, Sn, Pb, Sb, Bi, Si, P, B and the like. These may be mixed in anamount of from 0 to 30 mol % based on the transition metal.

As a preferred lithium-containing transition metal oxide positiveelectrode active material to be used in the present invention, it isdesirable to synthesize it by mixing If the compounds in such amountsthat the molar ratio of lithium compound/transition metal compound (theterm transition metal as used herein means at least one metal selectedfrom the group consisting of Ti, V, Cr, Mn, Fe, Co, Ni, Mo and W) inrespective total amounts becomes 0.3 to 2.2.

As a more preferred lithium-containing transition metal oxide positiveelectrode active material to be used in the present invention, it isdesirable to synthesize it by mixing the compounds in such amounts thatthe molar ratio of lithium compound/transition metal compound (the termtransition metal as used herein means at least one metal selected fromthe group consisting of V, Cr, Mn, Fe, Co and Ni) in respective totalamounts becomes 0.3 to 2.2.

As the more preferred lithium-containing transition metal oxide positiveelectrode active material to be used in the present invention, Li_(x)QO_(y) (Q mainly contains at least one transition metal selected fromthe group consisting of Co, Mn, Ni, V and Fe; x=0.02 to 1.2; Y=1.4 to 3)is desirable. As the Q, the transition metal may be mixed with Al, Ga,In, Ge, Sn, Pb, Sb, Bi, Si, P, B and the like. Their mixing ratio ispreferably 0 to 30 mol % based on the transition metal.

Examples of the most preferred lithium-containing transition metal oxidepositive electrode active material to be used in the present inventioninclude Li_(x) CoO₂, Li_(x) NiO₂, Li_(x) MnO₂, Li_(x) Co_(g) Ni_(1-g)O₂, Li_(x) Mn₂ O₄ and Li_(x) Co_(f) V_(1-f) O₂ (x=0.02 to 1.2, g=0.1 to0.9, f=0.9 to 0.98 and z=2.01 to 2.3).

Examples of the most preferred lithium-containing transition metal oxidepositive electrode active material to be used in the present inventioninclude Li_(x) CoO₂, Li_(x) NiO₂, Li_(x) MnO₂, Li_(x) Co_(g) Ni_(1-g)O₂, Li_(x) Mn₂ O₄ and Li_(x) Co_(f) V_(1-f) O₂ (x=0.02 to 1.2, g=0.1 to0.9, f=0.9 to 0.98 and z=2.02 to 2.3). In this case, the value xdescribed above is a value before the commencement of charging anddischarging and changes by the charging and discharging.

The positive electrode active material can be synthesized by a method inwhich the lithium compound and transition metal compound are mixed andcalcined or a method in which they are subjected to a solution reaction,of which the calcining method is particularly preferred. The calciningtemperature to be employed in the present invention may be such a degreethat a portion of the mixed compounds to be used in the presentinvention are decomposed and melted, and it may be preferably from 250to 2,000° C., more preferably from 350 to 1,500° C. In the practice ofcalcination, it is desirable to carry out pre-calcining at 250 to 900°C. The calcining time is preferably 1 to 72 hours, more preferably 2 to20 hours. Mixing of the materials may be carried out either by a drymethod or a wet method. In addition, annealing may be carried out at 200to 900° C. after calcination.

The calcining gas atmosphere is not particularly limited and may beeither an oxidizing atmosphere or a reducing atmosphere. Examples ofsuch the atmosphere includes air or a gas having optionally controlledoxygen concentration, or hydrogen, carbon monoxide, nitrogen, argon,helium, krypton, xenon, carbon dioxide or the like.

When the positive electrode material of the present invention issynthesized, chemical intercalation of lithium into a transition metaloxide may be effected preferably by allowing a lithium metal, lithiumalloy or butyl lithium to react with the transition metal oxide.

Though not particularly limited, the positive electrode active materialto be used in the present invention may have an average particle size ofpreferably from 0.1 to 50 μm. It is desirable that the volume ofparticles having a particle size of 0.5 to 30 μm is 95% or more. It ismore preferable that a group of particles having a particle size of 3 μmor less occupies 18% or less of the total volume and a group ofparticles having a particle size of from 15 μm to 25 μm occupies 18% orless of the total volume. Though not particularly limited, theseparticles may have a specific surface area of preferably from 0.01 to 50m² /g, more preferably from 0.2 to 1 m² /g, when measured by the BETmethod. It is desirable also that, when 5 g of the positive electrodeactive material is dissolved in 100 ml of distilled water, thesupernatant liquor has a pH value of 7 to 12.

In order to obtain a desired particle size, commonly known crushers andclassifiers can be used. For example, a mortar, a ball mill, a vibratingball mill, a vibrating mill, a satellite ball mill, a planetary ballmill, a spinning air flow jet mill, a sieve and the like can be used.

The positive electrode active material thus obtained by calcining may beused after washing with water, an acidic aqueous solution, an alkalineaqueous solution, an organic solvent, a water-containing organic solventand the like.

According to the present invention, a plurality of different positiveelectrode active materials may be used in combination. For example, amaterial which shows opposite expansion or shrinkage behavior at thetime of charging or discharging can be used.

Preferred examples of the positive electrode active material whichexpands at the time of discharging (at the time of lithium ionintercalation) and shrinks at the time of charging (at the time oflithium ion deintercalation) include spinel type lithium-containingmanganese oxides, and preferred examples of the positive electrodeactive material which shrinks at the time of discharging (at the time oflithium ion intercalation) and expands at the time of charging (at thetime of lithium ion deintercalation) include lithium-containing cobaltoxides. The spinel type lithium-containing manganese oxide has astructural formula of preferably Li_(2-x) Mn₂ O₄ (0≦x≦2), morepreferably Li_(1-x) Mn₂ O₄ (0≦x≦1). Preferred example of thelithium-containing cobalt oxide has a structure of Li_(1-x) CoO₂(0≦x≦1).

The negative electrode material to be used in the present invention is acompound capable of intercalating and deintercalating light metal ions.Particularly preferred are light metals, light metal alloys,carbonaceous compounds, inorganic oxides, inorganic chalcogenides, metalcomplexes and organic high molecular compounds. These may be used aloneor as a mixture thereof. Examples of such combination include a lightmetal with a carbonaceous compound, a light metal with an inorganicoxide and a light metal with a carbonaceous compound and an inorganicoxide. These negative electrode materials are desirable, because theyprovide high capacity, high discharge potential, high safety and highcycle characteristics.

Lithium is desirable as the light metal. Examples of the light metalalloy include a metal which forms alloy with lithium and alithium-containing alloy. Particularly preferred are Al, Al--Mn, Al--Mg,Al--Sn, Al--In and Al--Cd.

The carbonaceous compound is a compound selected from the groupconsisting of natural graphite, artificial graphite, carbon obtained byvapor phase growth and carbon obtained by calcining an organic material,and particularly a compound having a graphite structure is desirable. Inaddition, the carbonaceous compound may contain other compounds thancarbon, such as B, P, N, S, SiC and B₄ C, in an amount of 0 to 10% byweight.

As the elements which form oxides or chalcogenides, transition metals ormetal and metalloid elements of the groups 13 to 15 of the periodictable are desirable.

As the transition metal compound, single or composite oxides of V, Ti,Fe, Mn, Co, Ni, Zn, W and Mo or chalcogenides are particularlydesirable. A more preferred example is a compound represented by Li_(p)CO_(q) V_(1-q) O_(r) (wherein p=0.1 to 2.5, q=0 to 1, r=1.3 to 4.5)disclosed in JP-A-6-44,972.

The metal or metalloid compounds other than transition metals areselected from oxides of elements of the groups 13 to 15 of the periodictable, Al, Ga, Si, Sn, Ge, Pb, Sb and Bi, alone or as a combination oftwo or more, and chalcogenides.

Their preferred examples include Al₂ O₃, Ga₂ O₃, SiO, SiO₂, GeO, GeO₂,SnO, SnO₂, SnSiO₃, PbO, PbO₂, Pb₂ O₃, Pb₂ O₄, Pb₃ O₄, Sb₂ O₃, Sb₂ O₄,Sb₂ O₅, Bi₂ O₃, Bi₂ O₄, Bi₂ O^(SnSio) ₃, GeS, GeS₂, SnS, SnS₂, PbS,PbS₂, Sb₂ S₃, Sb₂ S₅, SnSiS₃ and the like. Also, these compounds mayform composite oxides with lithium oxide, such as Li₂ GeO₃ and Li₂ SnO₂.

It is desirable that the aforementioned composite chalcogen compoundsand composite oxides are mainly amorphous at the time of assembling intoa battery. The term "mainly amorphous" as used herein means that thecompound has a broad scattering zone having a peak at 20° to 40° as the2θ value when measured by an X-ray diffraction method using CuKα rays,which may have crystalline diffraction lines. Preferably, the moststrong strength among the crystalline diffraction lines found within 40°to 70° as the 2θ value is 500 times or less of the diffraction strengthof the peak of 20° to 40° as the 2θ value of the broad scattering zone,more preferably 100 times or less and most preferably 5 times or less,but it is most particularly desirable that the compound does not havecrystalline diffraction lines.

The aforementioned composite chalcogen compounds and composite oxidesare composite compounds comprising transition metals and elements of thegroups 13 to 15 of the periodic table, and composite chalcogen compoundsand composite oxides mainly comprising two or more elements selectedfrom the group consisting of B, Al, Ga, In, Tl, Si, Ge, Sn, Pb, P, As,Sb and Bi are more desirable.

Particularly preferred are composite oxides mainly comprising two ormore elements selected from the group consisting of B, Al, Si, Ge, Snand P.

These composite chalcogen compounds and composite oxides may containelements of the groups 1 to 3 of the periodic table or halogen elements,mainly for the purpose of modifying their amorphous structure. They mayalso contain transition metals.

Among the aforementioned negative electrode materials, amorphouscomposite oxides mainly comprising tin are preferred, which arerepresented by formula (1) or (2).

    SnM.sup.1.sub.a O.sub.t                                    (1)

In the above formula, M¹ represents two or more elements selected fromthe group consisting of Al, B, P, Si, Ge, elements of the groups 1, 2and 3 of the periodic table and halogen elements, a represents a numberof 0.2 to 3, and t represents a number of 1 to 7.

    Sn.sub.x T.sub.1-x M.sup.1.sub.a O.sub.t                   (2)

In the above formula, T represents a transition metal such as V, Ti, Fe,Mn, Co, Ni, Zn, W and Mo, x represents a number of 0.1 to 0.9, and M¹, aand t represent the same as defined in formula (1).

Among the compounds of (1), compounds of formula (3) are more desirable.

    SnM.sup.2.sub.b O.sub.t                                    (3)

In the above formula, M² represents two or more elements selected fromthe group consisting of Al, B, P, Si, Ge, elements of the groups 1, 2and 3 of the periodic table and halogen elements, b represents a numberof 0.2 to 3, and t represents a number of 1 to 7.

Among compounds of (3), compounds of formula (4) are further desirable.

    SnM.sup.3.sub.c M.sup.4.sub.d O.sub.t                      (4)

In the above formula, M³ represents at least one element selected fromthe group consisting of Al, B, P, Si and Ge, M⁴ represents at least oneelement selected from the group consisting of the elements of the groups1, 2 and 3 of the periodic table and halogen elements, c represents anumber of 0.2 to 2, d represents a number of 0.01 to 1, wherein0.2<c+d<3, and t represents a number of 1 to 7.

According to the present invention, an amorphous oxide mainly comprisingSn and Ge represented by formula (5) is particularly preferred.

    SnGe.sub.e M.sup.5.sub.f M.sup.4.sub.g O.sub.t             (5)

In the above formula, M⁵ represents at least one element selected fromthe group consisting of Al, P, B and Si, M⁴ represents at least oneelement selected from the group consisting of the elements of the groups1, 2 and 3 of the periodic table and halogen elements similar to thecase of formula (4), e represents a number of 0.001 to 1, f represents anumber of 0.2 to 2, g represents a number of 0.01 to 1, and t representsa number of 1.3 to 7.

The amorphous complex oxide of the present invention can be obtained byeither a calcining method or a solution method, but the calcining methodis more preferable. In the calcining method, it is desirable to obtainthe amorphous composite oxide by thoroughly mixing the oxides orcompounds of elements described in formula (1) and then calcining themixture.

As the calcining conditions, the temperature rise rate is preferablywithin the range of from 5° C. to 200° C. per minute, the calciningtemperature is preferably within the range of from 500 to 1,500° C. andthe calcining time is preferably within the range of from 1 to 100hours. Also, the temperature down rate is preferably within the range offrom 2° C. to 10⁷ ° C.

The temperature rise ratio according to the present invention is anaverage rate of temperature rise of from "50% of the calciningtemperature (expressed by °C.)" to "80% of the calcining temperature(expressed by °C.)", and the temperature down ratio according to thepresent invention is an average rate of temperature down of from "80% ofthe calcining temperature (expressed by °C.)" to "50% of the calciningtemperature (expressed by °C.)".

The temperature down may be effected by cooling the material in acalcining furnace or by once taking the material out of the calciningfurnace and then cooling for example by putting it into water. Alsouseful are ultra-quenching methods described in Ceramics Processing(page 217, 1987, edited by Gihodo), such as gun method, Hammer-Anvilmethod, slap method, gas atomize method, plasma spray method,centrifugal quenching method, melt drag method and the like.Alternatively, the cooling may be effected making use of the singleroller method or twin roller method described on page 172 of New GlassHandbook (ed. by Maruzen, 1991). When a material which melts during thecalcining is used, the material may be fed during the calcination whilecontinuously taking out the calcined product. In the case of a materialwhich melts during the calcination, it is desirable to stir the meltedsolution.

The calcining gas atmosphere is preferably an atmosphere having anoxygen content of 5% by volume or less, more preferably an inert gasatmosphere. Examples of the inert gas include nitrogen, argon, helium,krypton, xenon and the like. Most preferred inert gas is pure argon.

The compound to be used in the present invention may have an averageparticle size of preferably from 0.1 to 60 μm. More particularly, it isdesirable that the average particle size is 0.7 to 25 μm and that 60% ormore of the total volume is occupied by particles having a particle sizeof 0.5 to 30 μm. Also, it is desirable that a group of particles of thenegative electrode active material having a particle size of 1 μm orless occupies 30% or less of the total volume and a group of particleshaving a particle size of from 20 μm or more occupies 25% or less of thetotal volume. As a matter of course, particle size of the material to beused does not exceed thickness of the material mixture layer on one sideof the negative electrode.

In order to obtain a desired particle size, commonly known crushers andclassifiers can be used. For example, a mortar, a ball mill, a sandmill, a vibrating ball mill, a satellite ball mill, a planetary ballmill, a spinning air flow jet mill, a sieve and the like can be used.The pulverization may be effected by a wet method which is carried outin the presence of water or methanol or the like organic solvent, ifnecessary. In order to obtain a desired particle size, it is desirableto carry out classification. The classification method is notparticularly limited, and it can be made using a sieve, an airclassifier or the like, if necessary. The classification can be made byeither a dry method or a wet method.

The average particle size means median diameter of primary particles andis measured by a laser diffraction type particle size distributionmeasuring apparatus.

The thus obtained negative electrode material may be used after itswashing with water, an acidic aqueous solution, an alkaline aqueoussolution, an organic solvent or a water-containing organic solvent.

Examples of the negative electrode material of the present invention areshown below, though the present invention is not restricted by thesematerials.

SnAl₀.4 B₀.5 P₀.5 K₀.1 O₃.65, SnAl₀.4 B₀.5 P₀.5 Na₀.2 O₃.7, SnAl₀.4 B₀.3P₀.5 Rb₀.2 O₃.4,

SnAl₀.4 B₀.5 P₀.5 Cs₀.1 O₃.65, SnAl₀.4 B₀.4 P₀.4 O₃.2, SnAl₀.3 B₀.5 P₀.2O₂.7,

SnAl₀.3 B₀.5 P₀.2 O₂.7, SnAl₀.4 B₀.5 P₀.3 Ba₀.08 Mg₀.08 O₃.26,

SnAl₀.4 B₀.4 P₀.4 Ba₀.08 O₃.28, SnAl₀.4 B₀.5 P₀.5 O₃.6, SnAl₀.4 B₀.5P₀.5 Mg₀.1 O₃.7,

SnAl₀.5 B₀.4 P₀.5 Mg₀.1 F₀.2 O₃.65, SnB₀.5 P₀.5 Li₀.1 Mg₀.1 F₀.2 O₃.05,

SnB₀.5 P₀.5 K₀.1 Mg₀.05 F₀.1 O₃.05, SnB₀.5 P₀.5 K₀.05 Mg₀.1 F₀.2 O₃.03,

SnB₀.5 P₀.5 K₀.05 Mg₀.1 F₀.2 O₃.03, SnAl₀.4 B₀.5 P₀.5 Cs₀.1 Mg₀.1 F₀.2O₃.65,

SnB₀.5 P₀.5 Cs₀.05 Mg₀.05 F₀.1 O₃.03, SnB₀.5 P₀.5 Mg₀.1 F₀.1 O₃.05,SnB₀.5 P₀.5 Mg₀.1 F₀.2 O₃,

SnB₀.5 P₀.5 Mg₀.1 F₀.06 O₃.07, SnB₀.5 P₀.5 Mg₀.1 F₀.14 O₃.03, SnPBa₀.08O₃.58,

SnPK₀.1 O₃.55, SnPK₀.05 Mg₀.05 O₃.58, SnPCs₀.1 O₃.55, SnPBa₀.08 F₀.08O₃.54,

SnPK₀.1 Mg₀.1 F₀.2 O₃.55, SnPK₀.05 Mg₀.05 F₀.1 O₃.53, SnPCs₀.1 Mg₀.1F₀.2 O₃.55,

SnPCs₀.05 Mg₀.05 F₀.1 O₃.53, Sn₁.1 Al₀.4 B₀.2 Ba₀.08 F₀.08 O₃.54,

Sn₁.1 Al₀.4 B₀.2 P₀.6 Li₀.1 K₀.1 Ba₀.1 F₀.1 O₃.65, Sn₁.1 Al₀.4 B₀.4 P₀.4Ba₀.08 O₃.34,

Sn₁.1 Al₀.4 PCs₀.05 O₁.23, Sn₁.1 Al₀.4 PK₀.05 O₄.23, Sn₁.2 Al₀.5 B₀.3P₀.4 Cs₀.2 O₃.5,

Sn₁.2 Al₀.4 B₀.2 P₀.6 Ba₀.08 O₃.68, Sn₁.2 Al₀.1 B₀.2 P₀.6 Ba₀.08 F₀.08O₃.04,

Sn₁.2 Al₀.4 B₀.2 P₀.6 Mg₀.04 Ba₀.04 O₃.68, Sn₁.2 Al₀.4 B₀.3 P₀.5 Ba₀.08O₃.58,

Sn₁.3 Al₀.3 B₀.3 P₀.4 Na₀.2 O₃.3, Sn₁.3 Al₀.2 B₀.4 P₀.4 Ca₀.2 O₃.4,

Sn₁.3 Al₀.4 B₀.4 P₀.4 Ba₀.2 O₃.6, Sn₁.4 Al₀.4 PK₀.2 O₄.6, Sn₁.4 Al₀.2Ba₀.1 PK₀.2 O₄.45,

Sn₁.4 Al₀.2 Ba₀.2 PK₀.2 O₄.6, Sn₁.4 Al₀.4 Ba₀.2 PK₀.2 Ba₀.1 F₀.2 O₄.9,

Sn₁.4 Al₀.4 PK₀.3 O₄.65, Sn₁.5 Al₀.4 PK₀.2 O₄.4, Sn₁.5 Al₀.4 PK₀.1O₄.65,

Sn₁.5 Al₀.4 PCs₀.05 O₄.63, Sn₁.5 Al₀.4 PCs₀.05 Mg₀.1 F₀.2 O₄.63,

SnGe₀.001 P₀.1 B₀.1 K₀.5 O₁.65, SnGe₀.02 P₀.3 K₀.1 O₁.84, SnGe₀.02 P₀.15B₀.15 K₀.1 O₁.69,

SnGe₀.05 P₀.3 B₀.4 K₀.1 O₂.5, SnGe₀.05 P₀.8 K₀.1 O₃.15, SnGe₀.05 P₀.6B₀.3 Mg₀.1 K₀.1 O₃.8,

SnGe₀.05 P₀.5 B₀.5 Cs₀.05 K₀.05 O₃.15, SnGe₀.1 P₀.9 K₀.1 O₃.5,

SnGe₀.1 P₀.7 B₀.2 K₀.1 Mg₀.1 O₃.3, SnGe₀.1 P₀.5 B₀.5 Ba₀.05 K₀.1 O₂.3,

SnGe₀.1 P₀.5 B₀.5 Pb₀.05 K₀.1 O₂.3,

SnGe₀.1 P₀.5 B₀.5 Mg₀.05 K₀.15 O₃.325, SnGe₀.1 P₀.5 B₀.5 Mg₀.2 K₀.05O₃.425,

SnGe₀.1 P₀.5 B₀.5 Mg₀.01 O₃.201, SnGe₀.1 P₀.5 B₀.5 Al₀.03 Mg₀.1 K₀.1O₃.425,

SnGe₀.1 P₀.5 B₀.5 Mg₀.1 Li₀.1 O₃.35, SnSi₀.5 Al₀.1 B₀.2 P₀.1 Ca₀.4 O₃.1,

SnSi₀.4 Al₀.2 B₀.4 O₂.7, SnSi₀.5 Al₀.2 B₀.1 P₀.1 Mg₀.1 O₂.8, SnSi₀.6Al₀.2 B₀.2 O₂.8,

SnSi₀.5 Al₀.3 B₀.4 P₀.2 O₃.55, SnSi₀.5 Al₀.3 B₀.4 P₀.5 O₄.30, SnSi₀.6Al₀.1 B₀.1 P₀.3 O₃.25,

SnSi₀.6 Al₀.1 B₀.1 P₀.1 Ba₀.2 O₂.95, SnSi₀.6 Al₀.1 B₀.1 P₀.1 Ca₀.2O₂.95,

SnSi₀.6 Al₀.4 B₀.2 Mg₀.1 O₃.2, SnSi₀.6 Al₀.1 B₀.3 P₀.1 O₃.05, SnSi₀.6Al₀.2 Mg₀.2 O₂.7,

SnSi₀.6 Al₀.2 Ca₀.2 O₂.7, SnSi₀.6 Al₀.2 P₀.2 O₃, SnSi₀.6 B₀.2 P₀.2 O₃,

SnSi₀.8 Al₀.2 O₂.9, SnSi₀.8 Al₀.3 B₀.2 P₀.2 O₃.85, SnSi₀.8 B₀.2 O₂.9,

SnSi₀.8 Ba₀.2 O₂.8, SnSi₀.8 Mg₀.2 O₂.8, SnSi₀.8 Ca₀.2 O₂.8, SnSi₀.8 P₀.2O₃.1,

Sn₀.9 Mn₀.3 B₀.4 P₀.1 Ca₀.1 Rb₀.1 O₂.95, Sn₀.9 Fe₀.3 B₀.4 P₀.4 Ca₀.1Rb₀.1 O₂.95,

Sn₀.8 Pb₀.2 Ca₀.1 P₀.9 O₃.35, Sn₀.9 Mn₀.1 Mg₀.1 P₀.9 O₃.35,

Sn₀.2 Mn₀.8 Mg₀.1 P₀.9 O₃.35, Sn₀.7 Pb₀.3 Ca₀.1 P₀.9 O₃.35,

Chemical structure of these compounds obtained by calcining can becalculated by an inductive coupling plasma (ICP) emission spectralanalysis as a measuring method and from weight difference of powderbefore and after its calcining as a simplified method.

Intercalating amount of a light metal into the negative electrodematerial of the present invention may be approximate value of depositionpotential of the light metal, for example, preferably 50 to 700 mol %,more preferably 100 to 600 mol %, per negative electrode material. It isdesirable that its deintercalating amount is larger than theintercalating amount. Intercalation of the light metal may be effectedpreferably by an electrochemical, chemical or thermal method.Preferably, the electrochemical method may be effected byelectrochemically introducing a light metal contained in the positiveelectrode active material or by electrochemically introducing directlyfrom a light metal or its alloy. In the chemical method, the negativeelectrode material is mixed and contacted with a light metal or allowedto react with an organic metal such as butyl lithium or the like. Theseelectrochemical and chemical methods are desirable. Lithium or lithiumion is particularly desirable as said light metal.

Various elements can be contained in the negative electrode material ofthe present invention. For example, it may contain lanthanoid metals(Hf, Ta, W, Re, Os, Ir, Pt, Au and Hg) and dopants of various electricconductivity increasing compounds (for example, compounds of Sb, In andNb). These compounds may be added in an amount of preferably from 0 to 5mol %.

The surface of the positive electrode active material or negativeelectrode material of oxide to be used in the present invention can becoated with oxides whose chemical formulae are different from thepositive electrode active material or negative electrode material to beused. As such surface oxides, oxides containing a compound whichdissolves under both acidic and alkaline conditions are desirable. Metaloxides having high electronic conductivity are further desirable. Forexample, it is desirable to include dopants (for example, metals havingdifferent valency, halogen elements and the like in the case of oxides)into PbO₂, Fe₂ O₃, SnO₂, In₂ O₃, ZnO and the like or oxides thereof.Particularly preferred are SiO₂, SnO₂, Fe₂ O₃, ZnO and PbO₂.

Amount of the surface-treated metal oxide is preferably from 0.1 to 10%by weight, more preferably from 0.2 to 5% by weight, most preferablyfrom 0.3 to 3% by weight, based on said positive electrode activematerial or negative electrode material.

In addition to the above, the surface of the positive electrode activematerial or negative electrode material can be modified. For example,the surface of metal oxide may be treated with an esterificating agent,a chelating agent, a conductive high polymer, a polyethylene oxide orthe like.

Also, the surface of the negative electrode material can be modified.For example, it can be treated by arranging a layer of an ion conductivepolymer or polyacetylene. In addition, the positive electrode activematerial or negative electrode material may be passed through apurification step such as water washing.

The electrode material mixture can contain an electrically conductiveagent, a binder, a filler, a dispersing agent, an ion conductive agent,a pressure reinforcing agent, and various other additives.

The electrically conductive agent is not particularly limited, providedthat it is an electron conductive material which does not cause chemicalchanges in the assembled battery. In general, natural graphite (flakegraphite, scale graphite, earthy graphite or the like), artificialgraphite and the like graphites, acetylene black, Ketjen black, channelblack, furnace black, lamp black, thermal black and the like carbonblacks, carbon fiber, metal fiber and the like electrically conductivefibers, copper, nickel, aluminum, silver and the like metal powders,zinc oxide, potassium titanate and the like electrically conductivewhiskers, titanium oxide and the like electrically conductive metaloxides or polyphenylene derivatives and the like organic electricallyconductive materials are used alone or as a mixture thereof. Of theseconductive agents, acetylene black or combination use of graphite andacetylene black is particularly preferred. When a water-dispersedmixture material is prepared, it is desirable to disperse theelectrically conductive agent in water in advance.

Though not particularly limited, the electrically conductive agent maybe added in an amount of preferably from 1 to 50% by weight, morepreferably from 1 to 30% by weight. In the case of carbon or graphite,an amount of from 2 to 15% by weight is particularly preferred.

Examples of the binder include polysaccharides, thermoplastic resins andpolymers having rubber elasticity, which may be used alone or as amixture thereof. The preferred examples include starch, polyvinylalcohol, carboxymethylcellulose, hydroxypropylcellulose, regeneratedcellulose, diacetylcellulose, polyvinyl chloride, polyvinyl pyrrolidone,polytetrafluoroethylene, polyvinylidene fluoride, polyethylene,polypropylene, ethylene-propylenediene terpolymer (EPDM), sulfonatedEPDM, styrene butadiene rubber, polybutadiene, fluoroelastomer andpolyethylene oxide. When a polysaccharide or the like compound havingfunctional groups which react with lithium is used, it is desirable todeactivate such functional groups by adding an isocyanate group or thelike compound. Though not particularly limited, the binder may be addedin an amount of preferably from 1 to 50% by weight, more preferably from2 to 30% by weight. Distribution of the binder in the material mixturemay be either uniform or uneven. Preferred binder of the presentinvention is a polymer having a decomposition temperature of 300° C. ormore. Examples of such a type of polymer include polyethylene,polypropylene, polytetrafluoroethylene (PTFE), polyvinylidene fluoride(PVDF), tetrafluoroethylene-hexafluoropropylene copolymer (FEP),tetrafluoroethylene-perfluoroalkylvinyl ether copolymer (PFA),vinylidene fluoride-hexafluoropropylene copolymer, vinylidenefluoride-chlorotrifluoroethylene copolymer, ethylene-tetrafluoroethylenecopolymer (ETFE resin), polychlorotrifluoroethylene (PCTFE), vinylidenefluoride-pentafluoropropylene copolymer, propylene-tetrafluoroethylenecopolymer, ethylene-chlorotrifluoroethylene copolymer (ECTFE),vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer,vinylidene fluoride-perfluoromethylvinyl ether-tetrafluoroethylenecopolymer and the like.

The filler is not particularly limited, provided that it is a fibrousmaterial which does not cause chemical changes in the assembled battery.In general, fibers of polypropylene, polyethylene and the like olefinicpolymers and of glass, carbon and the like are used. Though notparticularly limited, the filler may be added in an amount of preferablyfrom 0 to 30% by weight.

As the ion conductive agent, materials known as inorganic and organicsolid electrolytes can be used, which will be described later in detailin relation to the electrolytic solution. The pressure reinforcing agentis an inner pressure increasing compound which will be described later,and its typical examples include carbonates.

The positive or negative electrode to be used in the nonaqueoussecondary battery of the present invention can be prepared by coating apositive electrode material mixture or negative electrode materialmixture on a current collector. In addition to the material mixturelayer containing positive electrode active material or negativeelectrode material, the positive and negative electrodes may furtherhave an undercoating layer which is introduced with the aim ofincreasing adhesiveness between the collector and mixture layer andimproving conductivity, as well as a protecting layer which isintroduced for the purpose of mechanically and chemically protecting themixture layer.

In addition to the positive electrode active material or negativeelectrode material, the positive and negative electrode mixturematerials may respectively contain an electrically conductive agent, abinder, a dispersing agent, a filler, an ion conductive agent, apressure reinforcing agent and various other additives. The undercoatinglayer and protective layer may contain particles of binder andelectrically conductive agent and particles having no conductivity.

The electrolyte comprises in general a solvent and a lithium salt (anionand lithium cation) which dissolves in the solvent. Examples of thesolvent include propylene carbonate, ethylene carbonate, butylenecarbonate, dimethyl carbonate, diethyl carbonate, methylethyl carbonate,γ-butyrolactone, methyl formate, methyl acetate, 1,2-dimethoxyethane,tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl sulfoxide,1,3-dioxolan, formamide, dimethylformamide, dioxolan, acetonitrile,nitromethane, ethylmonoglyme, phosphoric acid triester,trimethoxymethane, a dioxolan derivative, sulfolan,3-methyl-2-oxazolidinone, a propylene carbonate derivative, atetrahydrofuran derivative, ethyl ether, 1,3-propanesultone and the likeaprotic organic solvent, which may be used alone or as a mixture of twoor more. Examples of the anion of lithium salt which dissolves in thesesolvents include ClO₄ ⁻, BF₄ ⁻, PF₆ ⁻, CF₃ SO₃ ⁻, CF₃ CO₂ ⁻, AsF₆ ⁻,SbF₆ ⁻, (CF₃ SO₂)₂ N⁻, B₁₀ Cl₁₀ ²⁻, (1,2-dimethoxyethane)₂ ClO₄ ⁻, loweraliphatic carboxylic acid ion, AlCl₁₄ ⁻, Cl⁻, Br⁻, I⁻, anion of achloroborane compound and tetraphenyl boric acid ion, which may be usedalone or as a mixture of two or more. Among these, a cyclic carbonateand/or acyclic carbonate are particularly preferred. For example, it isdesirable to include diethyl carbonate, dimethyl carbonate andmethylethyl carbonate. Also, it is desirable to include ethylenecarbonate and propylene carbonate. In a preferred electrolyte, LiCF₃SO₃, LiClO₄, LiBF₄ and/or LiPF₆ is included in an electrolytic solutionprepared by mixing ethylene carbonate optionally with propylenecarbonate, 1,2-dimethoxyethane, dimethyl carbonate or diethyl carbonate.As the supporting salt, LiPF₆ is particularly preferred.

Amount of these electrolytes to be added to the battery is notparticularly limited and decided based on the amount of the positiveelectrode active material and negative electrode material and the sizeof battery.

Though not particularly limited, concentration of the supportingelectrolyte may be within the range of from 0.2 to 3 mols per 1 liter ofthe electrolytic solution.

The following solid electrolytes can be used in combination with theelectrolytic solution.

Solid electrolytes are divided into inorganic solid electrolytes andorganic solid electrolytes.

As the inorganic solid electrolytes, nitrides, halides and oxygen acidsalts of Li are well known. Particularly preferred among them are Li₃ N,LiI, Li₅ NI₂, Li₃ N-LiI-LiOH, Li₄ SiO₄, Li₄ SiO₄ -LiI-LiOH, xLi₃ PO₄-(1-x)Li₄ SiO₄, Li₂ SiO₃, phosphorous sulfide compounds and the like.

As the organic solid electrolyte, a polyethylene oxide derivative or apolymer containing said derivative, a polypropylene oxide derivative ora polymer containing said derivative, a polymer containing iondissociation groups, a mixture of a polymer containing ion dissociationgroups with the aforementioned aprotic electrolytic solution, aphosphoric acid ester polymer and a high molecular matrix materialcontaining an aprotic polar solvent are useful. As an alternativemethod, polyacrylonitrile may be added to an electrolytic solution. Alsoknown is a method in which inorganic and organic solid electrolytes arecombination-used.

Also, other compounds may be added to the electrolyte in order toimprove discharging and charging/discharging characteristics. Examplesof such compounds include pyridine, triethyl phosphite, triethanolamine,cyclic ether, ethylenediamine, n-glyme, hexaphosphoric triamide,nitrobenzene derivative, sulfur, quinone imine dye, N-substitutedoxazolidinone and N,N'-substituted imidazolidinone, ethylene glycoldialkyl ether, quaternary ammonium salt, polyethylene glycol, pyrrole,2-methoxyethanol, AlCl₃, monomer of electrically conductive polymerelectrode active material, triethylenephosphoramide, trialkylphosphine,morpholine, aryl compound having carbonyl group, crown ethers such as12-crown-4, hexamethylphosphoric triamide and 4-alkylmorpholine,bicyclic tertially amine, oil, quaternary phosphonium salt, tertiallysulfonium salt and the like.

In order to obtain a noncombustible electrolytic solution, ahalogen-containing solvent such as carbon tetrachloride, ethylenechloride trifluoride or the like can be contained in the electrolyticsolution. Also, carbon dioxide can be contained in the electrolyticsolution, in order to give high temperature preservation capacity.

In addition, an electrolytic solution or electrolyte can be contained inthe mixture of positive and negative electrode materials. For example, amethod is known in which the aforementioned ion conductive polymer ornitromethane or an electrolytic solution is contained.

As the separator, an insulating microporous thin film having large ionpermeability and desired mechanical strength is used. It is desirablethat such a film has a function to block its pores at 80° C. or more toincrease resistance. From the viewpoint of organic solvent resistanceand hydrophobic property, a sheet or nonwoven fabric prepared from anolefinic polymer such as polypropylene and/or polyethylene or glassfibers is used. With regard to the pore size of separator, the generallyused range of battery separator is used. For example, a range of from0.01 to 10 μm may be used. With regard to the thickness of separator,the generally used range of battery separator is used. For example, arange of from 5 to 300 μm may be used. The separator may be produced bysynthesizing a polymer and then making pores by a dry, drawing, solutionor solvent removing method or by a combination thereof.

As the current collector of electrode active material, any electronconductive material can be used, with the proviso that it does not causechemical changes in the assembled battery. For example, stainless steel,nickel, aluminum, titanium, carbon or the like, as well as aluminum orstainless steel whose surface is treated with carbon, nickel, titaniumor silver, is used as the material of the current collector in thepositive electrode. Aluminum or an aluminum alloy is particularlypreferred. In the negative electrode, stainless steel, nickel, copper,titanium, aluminum, carbon or the like, as well as copper or stainlesssteel whose surface is treated with carbon, nickel, titanium or silver,or an Al--Cd alloy is used as the material of the current collector inthe negative electrode. Of these materials, copper or a copper alloy isparticularly preferred. The surface of these materials may be oxidized.It is desirable to make rough on the current collector surface by asurface treatment. With regard to its shape, a foil, a film, a sheet, anet, a punched body, a lath body, a porous body, a foamed body, a moldedbody of fibers and the like can be used. Though not particularlylimited, it may have a thickness of from 1 to 500 μm.

The battery can be made into any shape such as a sheet shape, acylindrical shape, a flat shape, an angular shape or the like.

The material mixture of the positive electrode active material ornegative electrode material is mainly used by coating it on a currentcollector and drying and compressing thereafter. The coating can beeffected in the usual way. For example, a reverse roll method, a directroll method, a blade method, a knife method, an extrusion method, acurtain method, a gravure method, a bar method, a dip method and asqueeze method can be used. Of these methods, the blade, knife andextrusion methods are preferred. It is desirable that the coating iscarried out at a rate of from 0.1 to 100 m/minute. In that case,excellent surface conditions of the coated layer can be obtained byselecting the aforementioned coating method in response to the physicalsolution properties and drying property of the material mixture. Thecoating may be made on one side and then the other side or on both sidesat the same time. Also, the coating may be carried out continuously,intermittently or in a stripe fashion. Though thickness, length andwidth of the coated layer are decided depending on the size of battery,it is particularly desirable that the coated layer on one side has athickness of from 1 to 2,000 μm under a compressed condition afterdrying.

With regard to the drying or dehydration method of the sheet, generallyused methods can be employed. It is particularly desirable to use hotair, vacuum, infrared radiation, far infrared radiation, electron beamand low moisture air, alone or in a combination thereof. The temperaturemay be within the range of preferably from 80 to 350° C., morepreferably from 100 to 250° C. The water content is preferably 2,000 ppmor less in the whole battery, and, in the case of the positive electrodematerial mixture, negative electrode material mixture and electrolyte,it is desirable to control the water content in the positive andnegative electrode material mixture respectively to 500 ppm or less fromthe viewpoint of cycle characteristics.

Pressing of the sheet can be effected by generally used methods, and diepress method and calender press method are particularly preferred. Thepressure is not particularly limited, but a pressure of from 0.2 to 3t/cm² is desirable. Pressing rate of the calender press method ispreferably from 0.1 to 50 m/minute. The pressing temperature ispreferably from room temperature to 200° C. Ratio of the width of thenegative electrode sheet to that of the positive electrode sheet ispreferably 0.9 to 1.1. A ratio of 0.95 to 1.0 is particularly preferred.Ratio of the content of the positive electrode active material to thatof the negative electrode material cannot be defined because of thedifferences in the kinds of compounds and the mixture materialformulations, but can be set to an optimum value by taking the capacity,cycle characteristics and safety into consideration.

After laminating said material mixture sheets via a separator, thesesheets are coiled or folded and inserted into a case, the sheets and thecase are electrically connected, an electrolytic solution is injectedtherein and then a battery case is formed using a sealing plate. In thiscase, an explosion-proof valve can be used as the sealing plate. Inaddition to the explosion-proof valve, conventionally various well-knownsafety elements may be attached to the battery case. For example, afuse, a bimetal, a PTC element or the like can be used as a overcurrentpreventing element. Also, in addition to the explosion-proof valve, amethod in which a notch is made in the battery case, a method in which acrack is made in the gasket or a method in which a crack is made in thesealing plate can be employed as an inner pressure incrementcountermeasure. Also, a protecting circuit in which anovercharge/overdischarge countermeasure is integrated may be installedin a battery charger or independently connected. In addition, a methodin which electric current is blocked by the increase in the batteryinternal pressure may be employed as an overcharge countermeasure. Inthat case, a compound capable of increasing internal pressure can becontained in the material mixture or electrolyte. Examples of theinternal pressure increasing compound include Li₂ CO₃, LiHCO₃, Na₂ CO₃,NaHCO₃, CaCO₃, MgCO₃ and the like carbonates.

Metals and alloys having electric conductivity can be used in the caseand lead plate. For example, iron, nickel, titanium, chromium,molybdenum, copper, aluminum and the like metals or alloys thereof canbe used. Welding of the cap, case, sheet and lead plate can be effectedby well-known methods (for example, direct or alternating currentelectric welding, laser beam welding and ultrasonic welding). As theseal plate sealing agent, asphalt and the like conventionally well-knowncompounds and mixtures can be used.

The application of the nonaqueous secondary battery of the presentinvention is not particularly limited. For example, it is useful inelectronic equipment such as notebook size color personal computers,note book size monochromatic personal computers, sub-notebook sizepersonal computers, pen input personal computers, pocket size (palmtop)personal computers, notebook size word processors, pocket size wordprocessors, electron book players, pocket phones, wireless extensions ofkey telephone sets, pagers, handy terminals, portable facsimiles,portable copying machines, portable printers, headphone stereos, videocameras, liquid crystal TV sets, handy cleaners, portable CD systems,mini disk systems, electrical shavers, machine translation systems, landmobile radiotelephones, transceivers, electrical tools, electronicnotebooks, portable calculators, memory cards, tape recorders, radios,backup power sources, memory cards and the like. It is also useful innational life items such as automobiles, electrically powered vehicles,motors, lights, toys, family (home) computers, load conditioners, irons,watches, stroboscopic lamps, cameras and medical equipment (for example,pacemakers, hearing aids, massaging machines and the like). It can alsobe used in various types of military equipment and spacecraft equipment.In addition, it can also be used in combination with other secondarybatteries, solar batteries or primary batteries.

It is desirable to combine proper chemical materials and batteryconstituting parts of the present invention described in the foregoing,and it is particularly desirable that Li_(x) CoO₂ and Li_(x) Mn₂ O₄(wherein 0≦x≦1) as a positive electrode active material and acetyleneblack as a conductive agent are contained. The positive electrodecurrent collector is prepared from stainless steel or aluminum and has anet, sheet, foil, lath or the like shape. As the negative electrodematerial, it is desirable to use at least one compound selected from thegroup consisting of lithium metal, a lithium alloy (Li--Al), acarbonaceous compound, an oxide (LiCoVO₄, SnO₂, SnO, SiO, GeO₂, GeO,SnSiO₃ or SnSi₀.3 Al₀.1 B₀.2 P₀.3 O₃.2), a sulfide (TiS₂, SnS₂, SnS,GeS₂ or GeS) and the like. The negative electrode current collector isprepared from stainless steel or copper and has a net, sheet, foil, lathor the like shape. The material mixture to be used together with thepositive electrode active material or negative electrode material may bemixed with acetylene black, graphite or the like carbon material as anelectron conductive agent. As the binder, polyvinylidene fluoride,polyfluoroethylene or the like fluorine-containing thermoplasticcompound, acrylic acid-containing polymer, styrene butadiene rubber,ethylene propylene terpolymer and the like elastomers may be used aloneor as a mixture thereof. As the electrolytic solution, it is desirableto use ethylene carbonate, diethyl carbonate, dimethyl carbonate and thelike cyclic or acyclic carbonates or ethyl acetate and the like estercompounds in combination, using LiPF₆ as a supporting electrolyte andfurther mixing with LiBF₄, LiCF₃ SO₃ and the like lithium salts. As theseparator, it is desirable to use polypropylene or polyethylene singlyor in combination. The battery may have a cylindrical, flat or angularshape. It is desirable to equip the battery with a means to securesafety at the time of malfunction (for example, an internal pressurereleasing type explosion-proof valve, a current blocking type safetyvalve or a separator which increases resistant at a high temperature).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration showing a negative electrode sheet pressedwith lithium foil, which is used in Example 1.

FIG. 2 is a longitudinal sectional view of a general cylinder typebattery.

FIG. 3 is an illustration showing an example of the adhesion of Li foilpieces on the negative electrode sheet.

BEST MODE OF CARRYING OUT THE INVENTION

The following describes the present invention further in detail withreference to illustrative examples, but the present invention is notrestricted by these examples without overstepping the gist of theinvention.

EXAMPLE 1

Synthesis of Negative Electrode Material-a

An 80.8 g of SnO was dry-blended with 30 g of SiO₂, 5.1 g of Al₂ O₃,10.4 g of B₂ O₃ and 41.4 g of Sn₂ P₂ O₇, and the mixture was put into analuminum crucible and heated to 1,000° C. at a rate of 15° C./minute inan atmosphere of argon. After calcined at 1,000° C. for 12 hours, it wascooled down to room temperature at a rate of 10° C./minute and taken outfrom the calcining furnace to obtain a glassy compound. Said compoundwas roughly pulverized using a jaw crusher to obtain a roughlypulverized material having an average particle size of 80 μm. The thusroughly pulverized material was subjected to dry pulverization at roomtemperature using a spinning air flow type jet mill and then toclassification by a cyclone, thereby obtaining a negative electrodematerial-a having an average particle size of 5.3 μm.

When the thus obtained compound was analyzed by an X-ray diffractionmethod (Cu-Kα rays), crystal-specific peaks were not found. As a result,it is confirmed that it was an amorphous compound.

Also, measurement of the atomic composition of the thus synthesizedcompound by an inductive coupling plasma emission spectral analysisconfirmed that it was synthesized with the intended atomic compositionratio.

Synthesis of Negative Electrode Material-b

A 13.5 g of tin monoxide was dry-blended with 6.0 g of silicon dioxideusing a ball mill. Next, the mixture was put into an aluminum crucible,heated to 1,000° C. at a rate of 15° C./minute in an atmosphere of argonand then, after 12 hours of calcining at 1,000° C., cooled down to roomtemperature at a rate of 10° C./minute in an atmosphere of argon toobtain a glassy compound. Said compound was roughly pulverized using ajaw crusher to obtain a roughly pulverized material having an averageparticle size of 80 μm.

Thereafter, a negative electrode material-b having an average particlesize of 5.5 μm was obtained in the same manner as the case of thenegative electrode material-a. It was confirmed by the same techniquesof the case of the negative electrode material-a that said negativeelectrode material-b was amorphous and synthesized with the intendedatomic composition ratio.

Negative Electrode Material-c

A commercially available petroleum coke (PC--R, manufactured by NipponPetroleum) was used as a carbonaceous negative electrode material.

Negative Electrode Material-d

A commercially available silicon dioxide (silicic anhydride,manufactured by Wako Pure Chemical Industries) was used as a negativeelectrode material mainly comprising silicon.

The positive electrode active material used herein is a commercialproduct of LiCoO₂.

Electrolytic solutions of the following compositions were used in thisexample.

    ______________________________________                                        EC       DEC       BC    PC    LiPF.sub.6                                                                           LiBF.sub.4                              ______________________________________                                        (1)    2     8         0   0     1    M   0                                   (2)    2     8         0   0     0.95 M   0.05 M                              (3)    5     5         0   0     1    M   0                                   (4)    2     6         2   0     1    M   0                                   (5)    2     6         0   2     1    M   0                                   (6)    2     6         0   2     0.95 M   0.05 M                              ______________________________________                                         EC: ethylene carbonate                                                        DEC: diethyl carbonate                                                        BC: butylene carbonate                                                        PC: propylene carbonate                                                       Each number represents volume ratio and M represents mol/liter.          

A lithium foil of 200 μm in thickness and 39 mm in width was purchasedand used by cutting it to a predetermined length.

Preparation of Positive Electrode Sheet

As the positive electrode active material, LiCoO₂, acetylene black,polytetrafluoroethylene and sodium polyacrylate were mixed at a ratio of92:4:3:1 and kneaded using water as a medium, and the thus obtainedslurry was coated on both sides of an aluminum foil (support) currentcollector having a thickness of 20 μm. The thus coated material wasdried and then subjected to compression molding using a calender press,thereby obtaining a strip-shaped positive electrode sheet. A lead platewas attached to a terminal of the positive electrode sheet by spotwelding and then the sheet was subjected to heat treatment for 30minutes at 210° C. in dry air having a dew point of -40° C. or less.

Preparation of Sheets of the Present Invention

Negative Electrode Sheet (a-1) of the Present Invention

Each of various negative electrode materials prepared in accordance withthe aforementioned method, acetylene black, graphite, polyvinylidenefluoride and carboxymethylcellulose were mixed at a ratio of 84:3:8:4:1and kneaded using water as a medium to obtain a slurry. The thusobtained slurry was coated on both sides of a copper foil having athickness of 18 μm using a doctor blade coater, dried and then subjectedto compression molding using a calender press, and a lead plate wasattached to a terminal of the resulting sheet by spot welding. In thiscase, an uncoated portion of 4 cm in width was arranged on its outermostperipheral. Thereafter, the sheet was subjected to heat treatment for 30minutes at 210° C. in dry air having a dew point of -40° C. or less,thereby obtaining a strip-shaped negative electrode sheet. In this case,a lithium foil cut to 4.0 cm in width was pressed on said uncoatedportion using a roller. Conditions of the negative electrode sheetobtained in this manner are shown in FIG. 1. In FIG. 1, "a" is theoutermost peripheral of the negative electrode, "b" is a portion coatedwith the negative electrode material and "c" is a portion pressed with ametallic lithium foil.

Preparation of Sheet for Comparison Use (s-1)

A negative sheet was prepared in the same manner as the case of thesheet of the present invention, except that the metallic lithium foilwas not pressed.

Preparation of Sheet for Comparison Use (s-3)

Petroleum coak, acetylene black, polyvinylidene fluoride andcarboxymethylcellulose were mixed at a ratio of 92:3:4:1 and kneadedusing water as a medium to obtain a slurry. The thus obtained slurry wascoated on both sides of a copper foil having a thickness of 18 μm usinga doctor blade coater, dried and then subjected to compression moldingusing a calender press, and a lead plate was attached to a terminal ofthe resulting sheet by spot welding. In this case, an uncoated portionof 4 cm in width was arranged on its outermost peripheral. Thereafter,the sheet was subjected to heat treatment for 30 minutes at 210° C. indry air having a dew point of -40° C. or less, thereby obtaining astrip-shaped negative electrode sheet. In this case, a lithium foil cutto 0.6 cm in width was pressed on the uncoated portion (copper foilportion) of the thus obtained sheet using a roller.

Sheet for Comparison Use (s-4)

A negative sheet was prepared in the same manner as the case of thesheet for comparison use (s-3), except that the metallic lithium foilwas not pressed.

After laminating the prepared positive electrode sheet, a separator madeof a micro-porous polypropylene film in that order, they were coiled ina spiral form. In this case, they were coiled in such a way that theside on which the metallic lithium foil was pressed faced central partof the coiled group. The coiled group was put into a bottomed cylindertype battery case, which also serves as a negative electrode terminal,made of iron which has been plated with nickel. 2 cc of theaforementioned electrolytic solution was injected into the battery case.A battery cover having a positive electrode terminal was cramped via agasket 6 to produce a cylinder type battery. In this case, the positiveelectrode terminal was connected with the positive electrode sheet, andthe battery case with the negative electrode sheet, in advance usinglead terminals. A sectional view of the cylinder type battery is shownin FIG. 2. In this drawing, 7 represents an explosion-proof valve. Thebattery was then allowed to stand for 7 days at 40° C. to carry out thefollowing performance evaluation.

The thus prepared battery was subjected to one cycle of charging anddischarging at a charging final voltage of 4.15 V, a discharging finalvoltage of 2.8 V and a current density of 1 mA/cm². Ratio of thecharging capacity to the discharging capacity was used as a Coulombefficiency. Thereafter, charging and discharging was repeated 5 cyclesat a charging final voltage of 4.15 V, a discharging final voltage of2.8 V and a current density of 3.5 mA/c², and then the dischargingcapacity was measured as a value when charged to a charging finalvoltage of 4.15 V at a current density of 3.5 mA/cm² and then dischargedto a discharging final voltage of 2.8 V at a current density of 0.7mA/cm². The cycle test was evaluated at a charging final voltage of 4.15V, a discharging final voltage of 2.8 V and a current density of 3.5mA/cm². In this case, the cycle test was started from charging. Thecycle characteristics were expressed as the number of cycles when thedischarging capacity reached 70% of the first discharging. The resultsare shown in Tables 1 to 3.

                  TABLE 1                                                         ______________________________________                                        (s-1), (s-3) and (s-4) in Table 1 each represents a negative electrode        sheet.                                                                             Negative Ratio  Elec. Coulomb                                                                              Capacity                                                                             Cycle                                No.  material*1                                                                             *2     soln*3                                                                              eff.*4 (wh)   *5                                   ______________________________________                                        1    c (s-4)  1.45   (1)   0.80   1.21   220  C.E.                            2    c (s-4)  1.45   (3)   0.81   1.22   240  C.E.                            3    c (s-3)  1.16   (1)   0.98   1.34   210  C.E.                            4    c (s-3)  1.16   (3)   0.99   1.35   220  C.E.                            5    a (s-1)  5.7    (1)   0.55   2.20   384  C.E.                            6    a (s-1)  5.7    (2)   0.57   2.25   522  C.E.                            7    a (s-1)  5.7    (3)   0.54   2.18   403  C.E.                            8    a (s-1)  5.7    (4)   0.55   2.20   382  C.E.                            9    a (s-1)  5.7    (5)   0.55   2.20   567  C.E.                            10   a (s-1)  5.7    (6)   0.56   2.23   544  C.E.                            11   b (s-1)  5.7    (1)   0.56   2.30   256  C.E.                            12   b (s-1)  5.7    (2)   0.56   2.30   331  C.E.                            ______________________________________                                         *1: negative electrode material used,                                         *2: weight ratio of positive electrode active material to negative            electrode material,                                                           *3: electrolytic solution,                                                    *4: Coulomb efficiency,                                                       *5: cycle characteristics,                                                    C.E.: comparative example                                                     Nos. 1 and 2: Amount of LiCoO.sub.2 facing negative electrode is 3.36 g,      amount of carbon facing positive electrode is 2.31 g.                         Nos. 3 and 4: Amount of LiCoO.sub.2 facing negative electrode is 2.86 g,      amount of carbon facing positive electrode is 2.46 g, lithium foil cut to     0.7 cm is pressed.                                                            Nos. 5 to 16: Negative electrode material contained in unit battery is        1.36 g, and that of LiCoO.sub.2 is 7.75 g.                               

                  TABLE 2                                                         ______________________________________                                        (s-1) in Table 2 represents a negative electrode sheet.                            Negative Ratio  Elec. Coulomb                                                                              Capacity                                                                             Cycle                                No.  material*1                                                                             *2     soln*3                                                                              eff.*4 (wh)   *5                                   ______________________________________                                        13   b (s-1)  5.7    (3)   0.56   2.30   267  C.E.                            14   b (s-1)  5.7    (4)   0.54   2.28   243  C.E.                            15   b (s-1)  5.7    (5)   0.56   2.32   268  C.E.                            16   b (s-1)  5.7    (6)   0.55   2.30   241  C.E.                            17   a (s-1)  3.1    (1)   0.42   1.59   226  C.E.                            18   a (s-1)  3.1    (2)   0.41   1.57   226  C.E.                            19   a (s-1)  3.1    (3)   0.42   1.59   211  C.E.                            20   a (s-1)  3.1    (4)   0.43   1.60   217  C.E.                            21   a (s-1)  3.1    (5)   0.42   1.59   190  C.E.                            22   a (s-1)  3.1    (6)   0.41   1.57   201  C.E.                            23   b (s-1)  3.1    (1)   0.43   1.67   106  C.E.                            24   b (s-1)  3.1    (2)   0.41   1.65    98  C.E.                            ______________________________________                                         *1 to *5 and C.E.: see Table 1                                                Nos. 17 to 40: Negative electrode material contained in unit battery is       1.9 g, and that of LiCoO.sub.2 is 5.9 g.                                      Nos. 29 to 40: Lithium foil cut to 4.0 cm was pressed on negative             electrode collector sheet.                                               

                  TABLE 3                                                         ______________________________________                                             Negative                                                                      material*1                                                                             Ratio  Elec. Coulomb                                                                              Capacity                                                                             Cycle                                No.  (*6)     *2     soln*3                                                                              eff.*4 (wh)   *5                                   ______________________________________                                        25   b (s-1)  3.1    (3)   0.42   1.66   85   C.E.                            26   b (s-1   3.1    (4)   0.42   1.66   73   C.E.                            27   b (s-1   3.1    (5)   0.41   1.65   102  C.E.                            28   b (s-1)  3.1    (6)   0.42   1.66   86   C.E.                            29   a (a-1)  3.1    (1)   0.95   3.01   620  I.E                             30   a (a-1)  3.1    (2)   0.98   3.03   667  I.E                             31   a (a-1)  3.1    (3)   0.96   3.02   640  I.E                             32   a (a-1)  3.1    (4)   0.94   2.98   604  I.E                             33   a (a-1)  3.1    (5)   0.98   2.97   692  I.E                             34   a (a-1)  3.1    (6)   0.97   3.01   630  I.E                             35   b (a-1)  3.1    (1)   0.96   3.10   324  I.E.                            36   b (a-1)  3.1    (2)   0.94   3.09   302  I.E.                            37   b (a-1)  3.1    (3)   0.96   3.11   306  I.E.                            38   b (a-1)  3.1    (4)   0.96   3.11   319  I.E.                            39   b (a-1)  3.1    (5)   0.94   3.09   310  I.E.                            40   b (a-1)  3.1    (6)   0.96   3.11   321  I.E                             ______________________________________                                         *1 to *5, and C.E.: see Table 1, I.E.: inventive example, (*6): negative      electrode sheet,                                                              No. 41: Amount of LiCo.sub.2 facing negative electrode is 1.36 g, silicon     dioxide facing positive electrode is 3.02 g.                                  Nos. 42 and 43: Amount of LiCoO.sub.2 facing negative electrode is 0.82 g     silicon dioxide facing positive electrode is 3.15 g, lithium foil cut to      mm is pressed.                                                           

When a carbonaceous negative electrode material was used, a batteryhaving well-balanced cycle characteristics, capacity and the like wasobtained by using 1.45 times of the positive electrode active materialbased on the negative electrode material. In this case, the capacity wasaround 1.2 Wh as shown in Table 1, but improvement of the capacity bythe topping of lithium foil was merely about 0.1 Wh at the maximum.

When the negative electrode material "a" or "b" is used without applyingmetallic lithium foil, a battery having most improved balance of cycliccharacteristics with capacity can be obtained by using LiCoO₂ of thepositive electrode active material in an amount of 5.7 times (by weight)of said negative electrode material. The capacity is 2.2 Wh which ishigher than the case of carbonaceous negative electrode material by afactor of 1.0 Wh, but the Coulomb efficiency is around 0.55 which meansthat about half of the added LiCoO₂ is consumed by side reactions of thenegative electrode material (Nos. 5 to 16 in Table 2). However, in thebatteries of the present invention in which metallic lithium foil waspressed on the negative electrode sheet in such an amount that Coulombefficiency became around 1.0, ratio of the positive electrode activematerial to the negative electrode material was able to be reduced to3.1 as shown in Nos. 29 to 40 of Table 3. As the results, it was able tointroduce various negative electrode materials into batteries, and thecapacity was improved to a surprisingly high level of 36% (about 1.0Wh). More surprisingly, the cycle performance was also improved. On theother hand, when the ratio of positive electrode active material tonegative electrode material was set to 3.1 without applying metalliclithium foil, the capacity was reduced to 28% and the cycle performancewas also deteriorated as shown in Nos. 13 to 24 of Table 1.

JP-A-6-325765 discloses use of lithium or a lithium alloy in a system inwhich a lithium-containing silicon oxide or silicic acid salt is used asthe negative electrode material. Its specification discloses a method inwhich lithium foil punched into almost the same size of a pelletizednegative electrode material is directly pressed on the material in acoin type battery. In accordance with this method, a cylinder typebattery in which silicon dioxide was used in the negative electrodematerial was prepared, by pressing lithium foil directly on the coatedportion of the negative electrode material, and the battery performancewas evaluated. Another battery in which lithium foil was pressed on anuncoated portion of the outermost peripheral of the negative electrodematerial was prepared in the same manner of the present invention andevaluated in the same manner. As the results, the capacity when silicondioxide was used as the negative electrode material was 0.41 Wh as shownin No. 41 of Table 3. When pressed on the current collector metalsimilar to the case of the present invention, the capacity improved bythe introduction of lithium foil was merely 0.03 Wh at the maximum asshown in No. 42 of Table 3. Capacity improving effect was not found whenlithium foil was directly pressed on the negative electrode material.

EXAMPLE 2

Negative Electrode Material

The negative electrode materials "a" and "b" described in Example 1 wereused.

Preparation of Positive Electrode Sheet

Prepared in the same manner as described in Example 1. In this case,weight of LiCoO₂ on the positive electrode sheet was 5.9 g.

Preparation of Negative Electrode Sheet

Each of various negative electrode materials prepared in accordance withthe aforementioned method, acetylene black, graphite, polyvinylidenefluoride and carboxymethylcellulose were mixed at a ratio of 84:3:8:4:1and kneaded using water as a medium to obtain a slurry.

The thus obtained slurry was coated on both sides of a copper foilhaving a thickness of 18 μm using a doctor blade coater, dried and thensubjected to compression molding using a calender press, the resultingsheet was slit into a strip of 41 mm in width and 300 mm in length, anda lead plate was attached to a terminal of the negative electrode sheetby spot welding. Thereafter, the sheet was subjected to heat treatmentfor 30 minutes at 210° C. in dry air having a dew point of -40° C. orless, thereby obtaining a strip-shaped negative electrode sheet. Weightof the negative electrode material on the negative electrode sheet was1.9 g. A lithium foil having a thickness of 40 μm was cut to four pieceseach having 9 mm in width and 22 cm in length (correspond to 13.7 g/m²of negative electrode sheet), and two of them were pressed on each sideof the negative electrode sheet using a roller.

Preparation of Sheet for Comparison Use--1

A negative electrode sheet was prepared in the same manner as the caseof the sheet of the present invention, except that the metallic lithiumfoil was not pressed.

Preparation of Sheet for Comparison Use--2

A negative electrode sheet was prepared in the same manner as the caseof the present invention, except that a lithium foil having a thicknessof 100 μm was cut to four pieces each having 9 mm in width and 22 cm inlength (correspond to 34.3 g/m² of negative electrode sheet), and two ofthem were pressed on each side of the negative electrode sheet using aroller.

Preparation of Sheet for Comparison Use--3

When a nonaqueous secondary battery is produced using the negativeelectrode material "a" or "b" and the positive electrode active materialLiCoO₂, the ratio "positive electrode active material/negative electrodematerial" (to be referred to as "C/A" hereinafter) exerts greatinfluence upon the balance of cycle characteristics with capacity. Whenmetallic lithium foil is used in the aforementioned amount, C/A=3.1 isdesirable, but, when metallic lithium foil is not used, C/A=5.7 ratherthan C/A=3.1 is effective in obtaining a battery having most balancedcycle characteristics and capacity.

In order to correctly evaluate cycle characteristics and capacity of anonaqueous secondary battery produced using the negative electrodematerial "a" or "b" and the positive electrode active material LiCoO₂,but not using metallic lithium foil, the aforementioned electrode sheetwas adjusted to such a length that the negative electrode material andthe positive electrode active material LiCoO₂ became 1.36 g and 7.75 g,respectively, thereby obtaining a ratio of C/A=5.7.

Next, a battery was prepared in the same manner as described in Example1.

The thus prepared battery was subjected to one cycle of charging anddischarging at a charging final voltage of 4.15 V, a discharging finalvoltage of 2.8 V and a current density of 1 mA/cm². Ratio of thecharging capacity to the discharging capacity was used as a Coulombefficiency. Thereafter, charging and discharging was repeated 5 cyclesat a charging final voltage of 4.15 V, a discharging final voltage of2.8 V and a current density of 3.5 mA/cm², and then the dischargingcapacity was measured as a value when charged to a charging finalvoltage of 4.15 V at a current density of 3.5 mA/cm² and then dischargedto a discharging final voltage of 2.8 V at a current density of 0.7mA/cm². The cycle test was evaluated at a charging final voltage of 4.15V, a discharging final voltage of 2.8 V and a current density of 3.5mA/cm². In this case, the cycle test was started from charging. Thecycle characteristics were expressed as the number of cycles when thedischarging capacity reached 70% of the first discharging. The resultsare shown in Table 4. As is apparent from the results shown in Table 4,Nos. 1 and 2 in which 13.7 g/m² of lithium was pre-intercalated into thenegative electrode sheet are greatly superior in cycle characteristicsto Nos. 3 and 4 in which 34.3 g/m² of lithium was pre-intercalated intothe negative electrode sheet. In addition, they are excellent in Coulombefficiency, capacity and cycle characteristics which are the basicperformance as a practical battery, in comparison with the batteries inwhich lithium was not pre-intercalated into the negative electrodesheet, namely not only Nos. 5 and 6 which have the same construction butalso Nos. 7 and 8 which are batteries having an optimized C/A ratio of5.7 taking balance of cycle characteristics with capacity intoconsideration.

                                      TABLE 4                                     __________________________________________________________________________        Negative                                                                           Li *2   Coulomb                                                                             Capacity                                                                           Cycle Remarks                                     No. elec. *1                                                                           (g/m.sup.2)                                                                        C/A                                                                              (%) *3                                                                              (Wh) (time) *4                                                                           *5                                          __________________________________________________________________________    1   a    13.7 3.1                                                                              0.98  2.97 567   I.E.                                        2   b    "    "  0.94  2.87 518   "                                           3   a    34.3 "  0.83  2.44 158   C.E.                                        4   b    "    "  0.84  2.31 98    "                                           5   a    --   "  0.43  1.41 284   "                                           6   b    --   "  0.41  1.36 258   "                                           7   a    --   5.7                                                                              0.57  2.10 39    "                                           8   b    --   "  0.56  2.30 328   "                                           __________________________________________________________________________     *1: negative electrode material,                                              *2: amount of preintercalated lithium,                                        *3: Coulomb efficiency,                                                       *4: cycle characteristics,                                                    *5: I.E., inventive example; C.E., comparative example                   

EXAMPLE 3

A total of 25 Li foil pieces, each having a thickness of 40 μm, a widthof 3.9 mm and a length of 41 mm, were arranged on each side of the samenegative electrode sheet of Example 2 at regular intervals in a stripeshape (FIG. 3(b)) and adhered by pressing them with a roller(corresponding to 13.8 g/m² per negative electrode sheet). Using thethus obtained negative electrode sheet, batteries were prepared in thesame manner as described in Example 1 and allowed to stand at 40° C. for2 days to evaluate their performance in the same manner as described inExample 1. As the results, it was revealed that the batteries of Nos. 9and 10 shown in Table 5 have superior Coulomb efficiency, capacity andcycle characteristics in comparison with the comparative examples 7 and8 shown in Table 4 which have the same construction.

                                      TABLE 5                                     __________________________________________________________________________        Negative                                                                           Li *2   Coulomb                                                                             Capacity                                                                           Cycle Remarks                                     No. elec. *1                                                                           (g/m.sup.2)                                                                        C/A                                                                              (%) *3                                                                              (Wh) (time) *4                                                                           *5                                          __________________________________________________________________________    9   a    13.8 3.1                                                                              0.98  3.02 601   I.E.                                        10  b    "    "  0.95  2.93 557   "                                           __________________________________________________________________________     *1: negative electrode material,                                              *2: amount of preintercalated lithium,                                        *3: Coulomb efficiency,                                                       *4: cycle characteristics,                                                    *5: I.E., inventive example; C.E., comparative example                   

EXAMPLE 4

Through a polyethylene terephthalate (PET) sheet of 50 μm in thicknesswere bored rectangular holes of 4 mm×10 mm, 5 holes within 40 mm incross direction and 20 holes over 22 cm in longitudinal direction, 100holes in total. Next, the thus prepared sheet was interposed between thesame negative electrode sheet of Example 1 and a Li foil of 40 μm inthickness and compressed strongly with a roller to effect pressing ofthe Li foil on portions of the negative electrode sheet corresponding tothe holes bored through PET (corresponding to 13.8 g/m² per negativeelectrode sheet). The thus prepared batteries 11 and 12 and 13 and 14were allowed to stand at 40° C. for 2 days and at 40° C. for 15 days,respectively, to carry out performance evaluation in the same manner asdescribed in Example 1. As the results, it was confirmed that thesebatteries 11 to 14 as shown in Table 6 have superior Coulomb efficiency,capacity and cycle characteristics in comparison with the comparativeexamples 7 and 8 which have the same construction.

                                      TABLE 6                                     __________________________________________________________________________        Negative                                                                           Li *2   Coulomb                                                                             Capacity                                                                           Cycle Remarks                                     No. elec. *1                                                                           (g/m.sup.2)                                                                        C/A                                                                              (%) *3                                                                              (Wh) (time) *4                                                                           *5                                          __________________________________________________________________________    11  a    13.8 3.1                                                                              0.97  2.98 590   I.E.                                        12  b    "    "  0.94  2.90 544   "                                           13  a    "    "  0.98  3.00 590   "                                           14  b    "    "  0.95  2.93 545   "                                           __________________________________________________________________________     *1: negative electrode material,                                              *2: amouunt of preintercalated lithium,                                       *3: Coulomb efficiency,                                                       *4: cycle characteristics,                                                    *5: I.E., inventive; C.E., comparative example                           

EXAMPLE 5

A negative electrode sheet was prepared by calcining Sn₀.1 P₀.5 B₀.5Al₀.5 K₀.1 Mg₀.1 Ge₀.1 O₄.1 in the same manner as described in Example2. To this was adhered Li foil in the same manner as described inExample 2. As the results, they showed excellent Coulomb efficiency,capacity and cycle characteristics similar to the case of Example 3.

For the sake of comparison, petroleum coke, acetylene black,polyvinylidene fluoride and carboxymethylcellulose were mixed at aweight ratio of 92:3:4:1 and kneaded using water as the medium, and theresulting slurry was subjected to the same procedure of Example 2 toprepare a carbon negative electrode sheet and to obtain a battery. Whenamounts of the positive electrode active material and negative electrodematerial were optimized in this system, the capacity was 1.21 Wh and theroom temperature cycle characteristic was 220. When pressing of Li foilas a technique of the present invention was applied to the carbonnegative electrode sheet, increase in the capacity was only 0.1 Wh, andimprovement in the cycle characteristics was not found.

EXAMPLE 6 Synthesis Example

A 13.5 g portion of tin monoxide was dry-blended with 3.6 g of silicondioxide, 0.64 g of magnesium oxide and 0.69 g of boron oxide, and themixture was put into an aluminum crucible and heated to 1,000° C. at arate of 15° C./minute in an atmosphere of argon. After 10 hours ofcalcining at 1,200° C., this was cooled down to room temperature at arate of 10° C./minute, taken out from the furnace, roughly pulverizedand then pulverized using a jet mill to obtain SnSi₀.6 Mg₀.2 B₀.2 O₂.7(Compound 1-A) having an average particle size of 4.5 μm. When analyzedby an X-ray diffraction analysis using CuKα rays, it was found that thiscompound has a broad peak with the highest peak at 28° as the 2θ value,but with no crystalline diffraction lines within 40° to 70° as the 2θvalue.

The same procedure was repeated to obtain the following compounds bymixing respective materials in stoichiometric amounts, and calcining andpulverizing the mixtures. SnSi₀.8 Mg₀.2 O₂.8 (1-B), SnSi₀.6 Al₀.2 Mg₀.2O₂.7 (1-C), SnSi₀.6 P₀.2 Mg₀.2 O₂.9 (1-D), SnSi₀.6 Al₀.1 B₀.2 Mg₀.1O₂.75 (1-E) and SnSi₀.5 P₀.1 B₀.1 Mg₀.3 O₂.7 (1-F).

The Compound 1-A synthesized in Synthesis Example was used as a negativeelectrode material, and 88% by weight of the compound was mixed with 6%by weight of scale shape graphite and then with 4% by weight ofpolyvinylidene fluoride dispersed in water and 1% by weight ofcarboxymethylcellulose as binders and 1% by weight of lithium acetate,and the resulting mixture was kneaded using water as the medium toprepare a slurry. The thus prepared slurry was coated on both sides ofcopper foil having a thickness of 18 μm by an extrusion method to obtaina negative electrode a.

Negative electrodes b-1 to b-7 having auxiliary layers were obtained bymixing electrically conductive particles and the like ingredients atrespective ratio shown in Table 7, kneading the mixture using water asthe medium and then coating the resulting slurry on the negativeelectrode a in such an amount that thickness of the auxiliary layerafter drying became 10 μm.

Each of these negative electrodes a and b-1 to b-7 was dried, subjectedto compression molding using a calender press and then cut topredetermined width and length to obtain negative electrode sheets a andb-1 to b-7 in a strip form. Width and length of the negative electrodesheet were adjusted to such levels that coating amount of the Compound1-A became 1.9 g.

Each of the thus obtained negative electrode sheets was equipped with anickel lead plate by spot welding and subjected to dehydration dryingfor 30 minutes at 230° C. in the air having a dew point of -40° C. orless, and then 2 pieces of lithium foil, each having a thickness of 40μm, a length of 22 cm and a width of 9 mm, were pressed on each side ofthe thus treated negative electrode sheet using a roller.

As the positive electrode material, 87% by weight of LiCoO₂ was mixedwith 6% by weight of scale-form graphite, 3% by weight of acetyleneblack and, as binders, 3% by weight of polytetrafluoroethylene dispersedin water and 1% by weight of sodium polyacrylate, the mixture waskneaded using water as the medium and then the resulting slurry wascoated on both sides of aluminum foil having a thickness of 20 μm by theaforementioned method to obtain a positive electrode a.

Positive electrodes b-1 to b-7 having auxiliary layers were prepared bycoating respective slurries of electrically conductive particles and thelike having compositions shown in Table 1 on the positive electrode a insuch amount that the protective layer after drying became 15 μm, in thesame manner as the case of the negative electrodes.

These positive electrodes a and b-1 to b-7 were dried, pressed and thencut to obtain positive electrode sheets a and b-1 to b-7. Coating amountof LiCoO₂ on the positive electrode sheet was 5.9 g in weight. Each ofthe thus obtained positive electrode sheets was equipped with analuminum lead plate by spot welding and then subjected to dehydrationdrying for 30 minutes at 230° C. in dry air having a dew point of -40°C. or less.

Thickness of the positive electrode sheet a was 250 μm and that of thepositive electrode sheets b-1 to b-7 was 265 μm.

                  TABLE 7                                                         ______________________________________                                        (Compositions of auxiliary and protective layers)                                       Mixing ratio of solid component (wt %)                                        b-1  b-2    b-3    b-4  b-5  b-6  b-7                               ______________________________________                                        Conductive particles                                                          scale graphite 3.5 μm                                                                   2      0      0    2    20   20   35                             acetylene black 0.2 μm                                                                  0      2      0    0    0    0    0                              nickel powder 2.0 μm                                                                    0      0      2    0    0    0    0                              α-Alumina                                                                            87     87     87   0    78   0    63                             Zirconia     0      0      0    87   0    78   0                              Polyvinylidene                                                                             9      9      9    9    0    0    0                              fluoride                                                                      Carboxymethyl-                                                                             2      2      2    2    2    2    2                              cellulose                                                                     Total       100    100    100  100  100  100  100                             ______________________________________                                    

The aforementioned negative electrode sheets and positive electrodesheets were combined as shown in Table 2 to prepare a Battery A(comparative) and Batteries B (invention).

Ten batteries were prepared for each of the Battery A (comparative) andBatteries B-1 to B-6 (invention), charged to 4.15 V at 1 mA/cm² and thenstored at 60° C. for 3 weeks. After 3 weeks of the storage, open circuitvoltage of each battery was measured, with the results shown in Table 8.

                  TABLE 8                                                         ______________________________________                                                  Negative  Positive                                                                              Open    Voltage                                   Battery type                                                                            sheet *1  sheet *2                                                                              voltage *3                                                                            fluctuation *4                            ______________________________________                                        A (comparison)                                                                          a         a        0.87 V 0.41                                      B-1 (invention)                                                                         b-1       b-1     4.13    0.01                                      B-2 (invention)                                                                         b-2       b-2     4.12    0.01                                      B-3 (invention)                                                                         b-3       b-3     4.12    0.01                                      B-4 (invention)                                                                         b-4       b-4     4.11    0.01                                      B-5 (invention)                                                                         b-5       b-5     4.13    0.01                                      B-6 (invention)                                                                         b-6       b-6     4.12    0.01                                      B-7 (invention)                                                                         b-7       b-7     4.12    0.01                                      B-8 (invention)                                                                         b-1       a       4.10    0.02                                      B-9 (invention)                                                                         b-4       a       4.09    0.02                                      B-10 (invention)                                                                        b-5       a       4.08    0.03                                      B-11 (invention)                                                                        b-7       a       4.08    0.02                                      ______________________________________                                         *1: negative electrode sheet                                                  *2: positive electrode sheet                                                  *3: open circuit voltage, average value                                       *4: voltage fluctuation, standard deviation                              

The above results show that the batteries of the present invention areevidently small in the voltage drop during storage and their performancetherefore is stable.

EXAMPLE 7

A total of 300 copies of each of Batteries A and B-1 to B-11 of Example6 were prepared and charged to 4.15 V. When they were checked, 6 copiesof Battery A for comparison use were poorly charged, but all copies ofthe Batteries B-1 to B-11 of the present invention were fully chargedwhich clearly showed improvement of the generation of defectiveproducts.

EXAMPLE 8

When the same test of Example 6 was carried out by replacing thenegative electrode material 1-A used in Example 6 by other materials 1-Bto 1-F, almost the same results as in Example 6 were obtained.

EXAMPLE 9

Negative electrode sheets c-1 and c-2 were prepared in the same manneras the negative electrode sheets b-1 and b-7 of Example 6, except thatthickness of the auxiliary layer of b-1 and b-7 was changed to 6 μm.Batteries C-1 and C-2 were prepared from these negative electrode sheetsin combination with the positive electrode sheet a. When the same testof Example 1 was carried out using the thus prepared Batteries C-1 andC-2, their voltage drop after storage was small similar to the case ofthe battery B, thus showing their stable performance.

EXAMPLE 9'

When the test of Example 1 was repeated, except that 2 pieces of lithiumfoil having a thickness of 30 μm, a length of 22 cm and a width of 12 mmwere pressed on each side of the negative electrode sheet using aroller, almost the same effects of Example 6 were obtained.

EXAMPLE 10

The negative electrode sheets a and b-1 and positive electrode sheets aand b-1 of Example 6 were used, and one set of the negative electrodesheets a and b-1 were pressed with lithium foil under the sameconditions of Example 6, and the other set were used with no pressing.Batteries were prepared from these positive and negative electrodesheets by their combinations shown in the following table in the samemanner as described in Example 1 and charged to 4.15 V at 1 mA/cm² tomeasure their discharging capacity. The discharging capacity wasexpressed based on Battery D-1. Also, 300 copies of each battery wereprepared to find the number of defective batteries in the same manner asdescribed in Example 7. The results are shown in Table 9.

                  TABLE 9                                                         ______________________________________                                        Type of                                                                              Negative Negative  Positive                                                                            Capacity                                                                              Defective                             battery                                                                              sheet *1 Li *2     sheet *3                                                                            *4      battery *5                            ______________________________________                                        D-1    a        no        a     100     8/300                                 D-2    a        yes       a     140     7/300                                 D-3    b-1      no        b-1    96     0/300                                 D-4    b-1      yes       b-1   135     0/300                                 ______________________________________                                         *1, negative electrode sheet;                                                 *2, Li in negative electrode;                                                 *3, positive electrode sheet;                                                 *4, discharging capacity;                                                     *5, the number of defective batteries                                    

The above results show that Battery D-4 of the present invention hashigh discharging capacity and is excellent in production suitability.

EXAMPLE 11

Predetermined amounts of tin monoxide, alumina, boron oxide, tinpyrophosphate and magnesium fluoride were subjected to dry blending, andthe mixture was put into an aluminum crucible and heated to 1,000° C. ata rate of 15° C./minute in an atmosphere of argon. After 10 hours ofcalcining, this was cooled down to room temperature at a rate of 10°C./minute and taken out from the furnace. The thus obtained sample wasroughly pulverized and then pulverized using a jet mill to obtain powderof 6.5 μm in average particle size. When analyzed by an X-raydiffraction analysis using CuKα rays, it was found that this compoundhas a broad peak with the highest peak at around 28° as the 2θ value,but with no crystalline diffraction lines within 40° to 70° as the 2θvalue. Elemental analysis revealed that this compound is SnAl₀.1 B₀.5P₀.5 Mg₀.1 F₀.2 O₃.15 (Compound G).

A negative electrode sheet 6a was prepared in the same manner asdescribed in Example 6, except that Compound G was used in stead ofCompound 1-A of Example 6. Also, a negative electrode sheet 6b having anauxiliary layer was prepared in the same manner as the case of thenegative electrode sheet b-1. One set of the negative electrode sheets6a and 6b on which lithium foil was pressed under the same conditions ofExample 6 and another set with no pressing were prepared. Batteries wereprepared from these negative electrode sheets in combination with thepositive electrode sheet of Example 6 to carry out the same test ofExample 10, with the results shown in Table 10.

                  TABLE 10                                                        ______________________________________                                        Type of                                                                              Negative Negative  Positive                                                                            Capacity                                                                              Defective                             battery                                                                              sheet *1 Li *2     sheet *3                                                                            *4      battery *5                            ______________________________________                                        E-1    6a       no        a     100     7/300                                 E-2    6a       yes       a     142     7/300                                 E-3    6b       no        b-1    96     1/300                                 E-4    6b       yes       b-1   135     0/300                                 ______________________________________                                         *1, negative electrode sheet;                                                 *2, Li in negative electrode;                                                 *3, positive electrode sheet;                                                 *4, discharging capacity;                                                     *5, the number of defective batteries                                    

The above results show that Battery E-4 of the present invention hashigh discharging capacity and is excellent in production suitability.

EXAMPLE 12

Sn₁.0 P₀.5 B₀.5 Al₀.5 K₀.1 Mg₀.1 Ge₀.1 O₄.1 was calcined in the samemanner as described in Example 6, and a negative electrode sheet 7a wasprepared by repeating the procedure of Example 6 except that the justdescribed compound was used in stead of Compound 1-A of Example 6. Also,negative electrode sheets 7b-1 to 7b-7 having auxiliary layers wereprepared in the same manner as the case of sheets b-1 to b-7 of Example6, and the negative electrode sheets and positive electrode sheets wereused in combinations shown in Table 11. A total of 25 lithium foilpieces having a thickness of 40 μm, a width of 3.9 mm and a length of 41mm were arranged on each side of the negative electrode sheet at regularintervals in a stripe shape and pressed with a roller to effect theirpressing (corresponding to 13.8 g/m² per negative electrode sheet).Batteries were prepared using the thus obtained negative electrodesheets in the same manner as described in Example 1, allowed to stand at40° C. for 12 days and then checked for their performance in the samemanner as described in Example 6. As the results, as shown in Table 11,it was revealed that the batteries of the present invention are small inthe voltage drop during storage and their performance therefore isstable.

                  TABLE 11                                                        ______________________________________                                                  Negative  Positive                                                                              Open    Voltage                                   Battery type                                                                            sheet *1  sheet *2                                                                              voltage *3                                                                            fluctuation *4                            ______________________________________                                        F (comparison)                                                                          a         a        0.88 V 0.39                                      F-1 (invention)                                                                         7b-1      b-1     4.12    0.01                                      F-2 (invention)                                                                         7b-2      b-2     4.12    0.01                                      F-3 (invention)                                                                         7b-3      b-3     4.12    0.01                                      F-4 (invention)                                                                         7b-4      b-4     4.11    0.01                                      F-5 (invention)                                                                         7b-5      b-5     4.12    0.01                                      F-6 (invention)                                                                         7b-6      b-6     4.12    0.01                                      F-7 (invention)                                                                         7b-7      b-7     4.12    0.01                                      F-8 (invention)                                                                         7b-1      a       4.11    0.02                                      F-9 (invention)                                                                         7b-4      a       4.09    0.02                                      F-10 (invention)                                                                        7b-5      a       4.08    0.02                                      F-11 (invention)                                                                        7b-7      a       4.08    0.02                                      ______________________________________                                         *1: negative electrode sheet                                                  *2: positive electrode sheet                                                  *3: open circuit voltage, average value                                       *4: voltage fluctuation, standard deviation                              

EXAMPLE 13

A mixture consisting of 86 weight parts of SnB₀.2 P₀.5 K₀.1 Mg₀.1 Ge₀.1O₂.8 as a negative electrode material, 3 weight parts of acetylene blackas an electrically conductive agent and 6 weight parts of graphite wasfurther mixed with 4 weight parts of polyvinylidene fluoride and 1weight part of carboxymethylcellulose as binders and then kneaded usingwater as the medium to obtain a negative electrode mixture slurry. Saidslurry was coated on both sides of copper foil having a thickness of 10μm using an extrusion type coating machine and then dried, therebyobtaining a negative electrode material mixture sheet.

Next, 79 weight parts of α-alumina, 18 weight parts of graphite and 3weight parts of carboxymethylcellulose were kneaded by adding water asthe medium to obtain an auxiliary layer slurry. Said slurry was coatedon the just described negative electrode material mixture sheet, driedand then subjected to compression molding by a calender press, therebypreparing a strip-shaped negative electrode sheet precursor having athickness of 98 μm, a width of 55 mm and a length of 520 mm.

The negative electrode sheet precursor was equipped with a nickel leadplate by spot welding and then subjected to dehydration drying for 30minutes at 230° C. in the air having a dew point of -40° C. or less.

On each side of the thus obtained sheet were pressed 12 pieces oflithium foil (99.5% in purity) having a thickness of 40 μm which hasbeen cut to a size of 20 mm×55 mm. The pressing was carried out by oncetransferring the lithium foil pieces onto a polyethylene roller of 300mm in diameter and then applying a pressure of 5 kg/cm² to both sides ofthe sheet simultaneously. Covering ratio of the negative electrode sheetwith the lithium foil was 40%.

A mixture consisting of 87 weight parts of LiCoO₂ as a positiveelectrode active material, 3 weight parts of acetylene black as anelectrically conductive agent and 6 weight parts of graphite was furthermixed with 3 weight parts of Nipol1820B (manufactured by Nippon Zeon)and 1 weight part of carboxymethylcellulose as binders, and the mixturewas kneaded using water as the medium, thereby obtaining a positiveelectrode material mixture slurry.

Said slurry was coated on both sides of aluminum foil having a thicknessof 20 μm using an extrusion type coating machine, dried and thensubjected to compression molding by a calender press, thereby preparinga strip-shaped positive electrode sheet (1) having a thickness of 260μm, a width of 53 mm and a length of 445 mm. An aluminum lead plate waswelded to a tip of the positive electrode sheet which was then subjectedto 30 minutes of dehydration drying at 230° C. in dry air having a dewpoint of -40° C. or less.

After laminating the thus heat-treated positive electrode sheet (1), aseparator (3) made of a micro-porous polyethylene/polypropylene film,the negative electrode sheet (2) and the separator (3) in that order,they were coiled in a spiral form.

The thus coiled body was put into a bottomed cylinder type battery case(4), which also serves as a negative electrode terminal, made of ironwhich has been plated with nickel. As an electrolyte, 1 mol/liter ofLiPF₆ (in a 2:8 weight ratio mixture solution of ethylene carbonate anddiethyl carbonate) was injected into the battery case which was cooledat 0° C. A battery cover (5) having a positive electrode terminal wascramped via a gasket (6) to produce a cylinder type battery of 65 mm inheight and 18 mm in outer diameter (FIG. 1), namely Battery No. 1. Inthis case, the positive electrode terminal (5) was connected with thepositive electrode sheet (1), and the battery case (4) with the negativeelectrode sheet, in advance using lead terminals. In the drawing, (7) isan explosion-proof valve.

Thereafter, the thus prepared battery was charged to 3.2 V at 0.2 mA/cm²and then allowed to stand for 2 weeks at 50° C.

After completion of the storage, this was charged to 4.1 V at 1 mA/cm²and then discharged to 2.8 V at 1 mA/cm². This was again charged to 4.1V at 1 mA/cm² and then discharged to 2.8 V at 0.5 mA/cm² to calculateits discharging capacity. Thereafter, a cycle test of 4.1-2.8 V wascarried out at 5 mA/cm to measure capacity keeping ratio after 300cycles. The results are shown in Table 12.

EXAMPLE 14

Battery No. 2 was prepared by repeating the procedure of Example 13,except that 24 pieces of lithium foil having a size of 10 mm×55 mm wereused and transfer of the foil was carried out by a polyethylene boardtransfer (one side and then the other, transfer of 10 lithium foilpieces at one time), and its evaluation was carried out in the samemanner as described in Example 13.

The results are shown in Table 13.

EXAMPLE 15

Battery Nos. 3 to 15 were prepared in the same manner by changing size,shape, numbers and the like of lithium foil as shown in Table 12.Discharging capacity and cycle characteristics of these batteries wereevaluated in the same manner as described in Example 13.

The results are shown in Table 13.

Comparative Example 1

The same evaluation as in Example 13 was carried out by preparingBattery Nos. a to e in which lithium foil was not applied or coveringratio of the negative electrode sheet with lithium foil was smaller than10% or thickness of lithium foil was smaller than 5 μm or larger than150 μm.

The results are shown in Table 12.

                                      TABLE 12                                    __________________________________________________________________________        Pattern                                                                           Size of Li foil                                                                        Cover                                                                              Li foil                                                                            Capacity                                                                            Capacity                                     No. *1  (mm)     ratio                                                                              transfer                                                                           (mAH) *2                                                                            ratio *3                                     __________________________________________________________________________    1   stripe                                                                            20 × 55 × 0.04                                                             40%  roller                                                                             1605  81%                                          2   "   10 × 55 × 0.04                                                             "    board                                                                              1650  83%                                          3   "   80 × 55 × 0.04                                                             "    roller                                                                             1540  70%                                          4   "    4 × 55 × 0.04                                                             "    "    1665  85%                                          5   overall                                                                           520 × 55 × 0.02                                                            100% "    1710  81%                                          6   "   520 × 55 × 0.03                                                            "    "    1720  72%                                          7   stripe                                                                             8 × 55 × 0.03                                                             60%  "    1550  80%                                          8   "    8 × 55 × 0.03                                                             "    board                                                                              1510  83%                                          9   "    10 × 55 × 0.075                                                           20%  roller                                                                             1620  74%                                          10  frame                                                                             10 × 20 × 0.05                                                             30%  "    1505  80%                                          11  "   5 × 10 × 0.1                                                               15%  "    1575  71%                                          12  stripe                                                                             2 × 55 × 0.05                                                             35%  "    1640  83%                                          13  "    4 × 55 × 0.08                                                             20%  board                                                                              1600  77%                                          14  disc                                                                              10 mm × 0.08 mm                                                                  "    roller                                                                             1525  74%                                          15  "   20 mm × 0.05 mm                                                                  30%  "    1580  82%                                          a   none                                                                              --       --   --   1120  84%                                          b   stripe                                                                            20 × 55 × 0.18                                                             10%  roller                                                                             1480  52%                                          c   "   20 × 55 × 0.2                                                               4%  "    1310  45%                                          d   "    4 × 55 × 0.18                                                             30%  "    1425  43%                                          e   frame                                                                             10 × 20 × 0.05                                                              4%  board                                                                              1250  68%                                          __________________________________________________________________________     *1, laminating pattern of lithium foil;                                       *2, discharging capacity;                                                     *3, keeping ratio of capacity after 300 cycles                           

As is apparent from the results shown in Table 12, batteries in whichlithium foil having a thickness of from 5 to 150 μm is laminated on thenegative electrode sheet in at least one pattern selected from overall,stripe, frame and disc shapes at a covering ratio of 10 to 100% havelarge discharging capacity and excellent cycle characteristics ascompared with other batteries in which lithium foil is not laminated orits thickness or covering ratio is outside the above ranges.

EXAMPLE 16

A cylinder type battery was prepared in the same manner as described inExample 13.

After completion of cramping, the thus prepared battery was subjected toaging at 0° C. for 2 hours and then at 25° C. for 15 hours, charged to aconstant voltage of 3.1 V at 0.4 mA/cm² and at 25° C. and then storedfor 2 weeks at 50° C. Voltage of this battery after 3 days of the agingwas 2.58 V.

After completion of the storage, this was charged to 4.1 V at 1 mA/cm²and then discharged to 2.8 V at 1 mA/cm². This was again charged to 4.1V at 1 mA/cm² and then discharged to 2.8 V at 0.5 mA/cm² to calculateits discharging capacity. Thereafter, a cycle test of 4.1-2.8 V wascarried out at 2.5 mA/cm² to measure capacity keeping ratio after 300cycles. The results are shown in Table 13.

The term "pre-charge" shown in Table 13 means the just describedcharging procedure.

EXAMPLE 17

After completion of steps until cramping in the same manner as describedin Example 16, the thus prepared battery was subjected to aging at 0° C.for 2 hours and then at 25° C. for 15 hours, and a cycle of 3.1-2.7 Vwas repeated 50 times at 0.75 mA/cm² and at 25° C. (this was carried outby a combination of constant voltage charging and constant voltageconstant current discharging). Voltage of this battery after 3 days ofthe aging was 2.85 V.

Thereafter, evaluation of this battery was carried out in the samemanner as described in Example 16. The results are shown in Table 14.

The term "pre-charge/discharge" shown in Table 14 means the justdescribed charge/discharge cycle procedure.

EXAMPLE 18

A battery was prepared and its pre-charge was carried out in the samemanner as in the Example 16 except that SnB₀.2 P₀.5 K₀.1 Ge₀.1 O₂.7S₀.02 (6.8 μm in average particle size) was used as a negative electrodematerial. Thereafter, the evaluation was carried out in the same manneras in Example 1. The results are shown in Table 15.

                                      TABLE 13                                    __________________________________________________________________________    Pre-charge conditions      Discharge                                                                             Capacity                                       25° C.                                                                     heat V  cur time                                                                             Volt                                                                              capacity                                                                              ratio                                      No. *1  *2   *3 *4  (h)                                                                              *5  (mAh) *6                                                                              (%) *7                                     __________________________________________________________________________    1   15  --   3.1                                                                              0.4 2  2.58                                                                              1600    81                                         2   75  --   3.1                                                                              0.4 2  2.53                                                                              1585    82                                         3   15  50° C.                                                                      3.1                                                                              0.4 2  2.61                                                                              1610    84                                                 /48 h                                                                 4   15  --   3.4                                                                              0.4 2  3.01                                                                              1560    79                                         5   15  --   2.2                                                                              0.4 2  1.70                                                                              1490    75                                         6   15  --   3.7                                                                              0.4 4  3.41                                                                              1425    75                                         7   15  --   3.1                                                                              0.1 2  2.55                                                                              1625    83                                         8   15  --   3.1                                                                              1.2 2  2.60                                                                              1590    78                                         9   15  --   3.1                                                                              2.7 2  2.85                                                                              1610    75                                         10  240 --   3.1                                                                              0.4 2  2.41                                                                              1570    80                                         11  480 --   3.1                                                                              0.4 2  2.28                                                                              1555    79                                         12   1  --   3.1                                                                              0.4 2  2.55                                                                              1595    75                                         a   --  --   -- --  -- 0.85                                                                              1375    70                                         b   0.5 --   1.7                                                                              0.4 2  1.35                                                                              1400    71                                         c   15  --   1.1                                                                              0.2 2  0.91                                                                              1390    70                                         d   15  --   4.1                                                                              2.7 1  3.85                                                                              1480    65                                         __________________________________________________________________________     *1, aging time at 25° C. until precharging;                            *2, condition of heat aging until precharging;                                *3, voltage setting (V);                                                      *4, current value (mA/cm.sup.2);                                              *5, voltage (V) of battery 3 days after precharging;                          *6, discharging capacity (mAh);                                               *7, capacity keeping ratio (%) after 300 cycles                          

                                      TABLE 14                                    __________________________________________________________________________    Pre charge/discharge conditions                                                                            Discharge                                                                          Capacity                                        25° C.                                                                     heat                                                                              V-1                                                                              V-2 cur                                                                              cycle                                                                            Volt                                                                              capacity                                                                           ratio                                       No. *1  *2  *3 *4  *5 *6 *7  *8   *9                                          __________________________________________________________________________    1   15  --  3.1                                                                              2.7 0.75                                                                             50 2.85                                                                              1610 83                                          2   15  50° C.                                                                     3.1                                                                              2.7 0.75                                                                             50 2.88                                                                              1595 83                                                  /72 h                                                                 3   15  --  3.3                                                                              2.5 0.75                                                                             50 2.95                                                                              1600 81                                          4   15  --  2.5                                                                              1.8 0.75                                                                             50 2.30                                                                              1580 80                                          5   15  --  1.8                                                                              1.2 0.75                                                                             100                                                                              1.51                                                                              1550 75                                          6   15  --  3.5                                                                              3.0 0.75                                                                             50 3.28                                                                              1520 80                                          7   15  --  3.1                                                                              2.7 0.25                                                                             50 2.77                                                                              1600 80                                          8   15  --  3.1                                                                              2.7 2.7                                                                              50 2.70                                                                              1570 81                                          9   15  --  3.1                                                                              2.7 0.75                                                                             100                                                                              2.88                                                                              1610 82                                          10  15  --  3.1                                                                              2.8 0.5                                                                              10 2.80                                                                              1575 79                                          11  240 --  3.2                                                                              2.5 0.75                                                                             100                                                                              2.91                                                                              1600 78                                          12   2  50° C.                                                                     3.1                                                                              2.7 0.75                                                                             50 2.78                                                                              1570 80                                                  /2 h                                                                  a   15  --  1.6                                                                              1.0 0.75                                                                             50 1.35                                                                              1490 72                                          b   15  --  1.2                                                                              0.5 0.75                                                                             50 0.82                                                                              1380 78                                          c   15  --  4.1                                                                              2.5 5.0                                                                              50 3.90                                                                              1495 68                                          d   15  --  4.1                                                                              3.8 0.75                                                                             750                                                                              3.92                                                                              1310 67                                          __________________________________________________________________________     *1, aging time at 25° C. until precharge/discharge;                    *2, condition of heat aging until precharge/discharge;                        *3, charging voltage (V);                                                     *4, discharging voltage (V);                                                  *5, current value (mA/cm.sup.2);                                              *6, the number of cycles (times);                                             *7, voltage (V) of battery 3 days after precharge/discharge;                  *8, discharging capacity (mAh);                                               *9, capacity keeping ratio (%) after 300 cycles                          

                  TABLE 15                                                        ______________________________________                                             Ag-    Setting                  Discharge                                                                            Capacity                               ing    Voltage Current                                                                              Time Volt.                                                                              capacity                                                                             ratio                             No.  *1     (V)     (mA/cm.sup.2)                                                                        (h)  (V)*2                                                                              (mAh)  (%) *3                            ______________________________________                                        1    15     3.1     0.3    2    2.52 1620   83                                2    15     2.5     0.3    2    2.12 1600   79                                3     3     3.4     1.1    1    3.19 1585   79                                4    240    3.1     0.2    5    2.68 1605   82                                5    15     2.0     0.4    2    1.67 1590   79                                6    10     3.8     0.5    3    3.52 1570   78                                a    --     --      --     --   0.72 1350   72                                b    15     1.5     0.4    2    1.10 1430   73                                ______________________________________                                         *1, aging time at 25° C. until precharge;                              *2, voltage of battery 3 days after precharge;                                *3, capacity keeping ratio after 300 cycles                              

As is apparent from the results shown in Tables 13 to 15, batteries inwhich their voltage is adjusted to 1.5 to 3.8 by carrying out at leastone cycle of charging or charging and discharging during their aginghave large discharge capacity and excellent cycle characteristics ascompared with other batteries having a voltage of smaller than 0.5 V orlarger than 3.8 V.

INDUSTRIAL APPLICABILITY

A nonaqueous secondary battery having high capacity, high energy densityand high cycle characteristics can be obtained by the use of a compositeoxide or composite chalcogen negative electrode material capable ofintercalating and deintercalating lithium in which, like the case of thepresent invention, a metal foil mainly comprising lithium is pressed onthe negative electrode sheet to effect pre-intercalation of lithium intothe negative electrode material.

We claim:
 1. A nonaqueous secondary battery which comprises:a positiveelectrode sheet having a layer mainly comprising a lithium-containingmetal oxide; a negative electrode sheet having (1) a layer mainlycomprising at least one compound selected from the group consisting of ametal oxide, a metalloid oxide, a metal chalcogenide and a metalloidchalcogenide which are capable of intercalating and deintercalatinglithium, (2) at least one auxiliary layer containing water-insolubleelectrically conductive particles provided on said layer (1), and (3) ametal material film mainly comprising lithium laminated on saidauxiliary layer (2); an electrolytic solution containing a lithium salt;and a separator, wherein said auxiliary layer is laminated with saidmetal material film mainly comprising lithium either:(i) wholly, or (ii)partially in at least one pattern selected from the group consisting ofstripe, frame, and disc shapes.
 2. The nonaqueous secondary battery asin claim 1, wherein the metal material mainly comprising lithium has acovering ratio on said auxiliary layer of 10 to 100%.
 3. The nonaqueoussecondary battery as in claim 1, wherein the metal material mainlycomprising lithium has a covering ratio on said auxiliary layer of 20 to100%.
 4. The nonaqueous secondary battery as in claim 1, wherein saidmetal material mainly comprising lithium has a thickness of 5 to 150 μm.5. The nonaqueous secondary battery as in claim 1, wherein the waterinsoluble particles present in said auxiliary layer are a mixture ofelectrically conductive particles and other particles havingsubstantially no electrical conductivity.
 6. The nonaqueous secondarybattery as in claim 1, wherein said auxiliary layer has a thickness of0.2 to 40 μm.
 7. The nonaqueous secondary battery as in claim 1, whereinsaid auxiliary layer has a thickness of 0.3 to 20 μm.
 8. The nonaqueoussecondary battery as in claim 1, wherein said layer mainly comprising ametal or metalloid oxide and/or a chalcogenide comprises atin-containing composite oxide and/or composite chalcogen compound. 9.The nonaqueous secondary battery as in claim 8, wherein saidtin-containing composite oxide is represented by formula (1)

    SnM.sup.1.sub.a O.sub.t                                    ( 1)

wherein M¹ represents two or more elements selected from the groupconsisting of Al, B, P, Si, Ge, elements of Groups 1, 2 and 3 of theperiodic table and halogen, a represents a number of 0.2 to 3, and trepresents a number of 1 to
 7. 10. The nonaqueous secondary battery asin claim 8, wherein said tin-containing composite oxide is representedby formula (4)

    SnM.sup.3.sub.c M.sup.4.sub.d O.sub.t                      ( 4)

wherein M³ represents at least one element selected from the groupconsisting of Al, B, P, Si and Ge, M⁴ represents at least one elementselected from the group consisting of elements of Groups 1, 2 and 3 ofthe periodic table and halogen, c is a number of 0.2 to 2, d representsa number of 0.01 to 1, wherein 0.2<c+d<3, and t represents a number of 1to
 7. 11. The nonaqueous secondary battery as in claim 1, wherein saidnonaqueous secondary battery is a cylindrical battery.
 12. A method forproducing a nonaqueous secondary battery which comprises:a positiveelectrode sheet having a layer mainly comprising a lithium-containingmetal oxide; a negative electrode sheet having (1) a layer mainlycomprising at least one compound selected from the group consisting of ametal oxide, a metalloid oxide, a metal chalcogenide and a metalloidchalcogenide which are capable of intercalating and deintercalatinglithium, (2) at least one auxiliary layer containing water-insolubleelectrically conductive particles provided on said layer (1), and (3) ametal material film mainly comprising lithium laminated on saidauxiliary layer (2); an electrlytic solution containing a lithium salt;and a separator;said method comprising: laminating (1) a layer mainlycomprising at least one compound selected from the group consisting of ametal oxide, a metalloid oxide, a metal chalcogenide and a metalloidchalcogenide which are capable of intercalating and deintercalatinglithium, (2) at least one auxiliary layer containing water-insolubleelectrically conductive particles, and (3) a metal material film mainlycomprising lithium in said order; and aging after injection of theelectrolytic solution so that lithium is pre-intercalated into thenegative electrode sheet, wherein said auxiliary layer is laminated withsaid metal material film mainly comprising lithium either:(i) wholly, or(ii) partially in at least one pattern selected from the groupconsisting of stripe, frame, and disc shapes.
 13. The method forproducing a nonaqueous secondary battery as in claim 12, wherein saidprocess comprises electrochemically pre-intercalating, into saidnegative electrode sheet, lithium in an amount of 1 to 30 g/m².
 14. Themethod for producing a nonaqueous secondary battery as in claim 12,wherein, in said aging, the aging temperature is from 0 to 80° C. andthe aging period is from 1 hour to 60 days.
 15. The method for producinga nonaqueous secondary battery as in claim 12, wherein in said aging,the aging temperature is from 20 to 70° C. and the aging period is from3 to 30 days.
 16. The method for producing a nonaqueous secondarybattery as in claim 12, wherein in said laminating of the metal materialmainly comprising lithium on said auxiliary layer is by a roll transfermethod or a board transfer method.
 17. The method for producingnonaqueous secondary battery as in claim 12, wherein said nonaqueoussecondary battery is a cylindrical battery.